# About SunScope

See the sun the way your skin does.

## What is SunScope?

SunScope is a free outdoor thermal comfort forecast that goes well beyond standard air temperature. Most weather apps tell you it's 12 °C and leave you to guess whether that means a t-shirt or a heavy coat. SunScope combines air temperature, humidity, wind speed, and solar radiation into a single felt temperature — so you know what to actually expect when you step outside.

The core calculation is the Universal Thermal Climate Index (UTCI), a peer-reviewed biometeorological standard developed by Bröde et al. (2012) and used globally in heat-health warning systems and urban planning. On top of that, SunScope builds its own SunSoak index — because UTCI alone doesn't account for the full picture of where you actually are and what the weather is actually doing to you. SunSoak layers three extra dimensions on top of UTCI: a rain and snow penalty for the chill of wet clothing and skin; an environment modifier that adjusts the solar and thermal load for your surroundings (forest canopy, alpine altitude, lakeside glare, shaded riverbank, desert ground heat); and the full radiant heat absorbed from surrounding surfaces. One number that honestly answers: what will my body actually feel out there?

Forecast data is sourced in real time from Open-Meteo, a free and open-source weather API drawing on ECMWF and national meteorological services. The forecast refreshes automatically every five minutes and is available for any location worldwide.

## What else does SunScope calculate?

SunScope goes far beyond a single felt-temperature number. Depending on the profile you choose, it can calculate and display a wide range of derived quantities, each built on the same per-hour weather data:

Vehicle interior temperature. A physics-based model estimates how hot a sealed, parked vehicle gets over time — combining heat conducted through the roof and body panels with direct solar gain through the side windows. You can select your vehicle type (car, MPV, SUV, motorhome, or caravan), each of which has its own albedo, glazing area, and insulation characteristics. A Windows open toggle switches to a ventilated model where convective loss is roughly five times higher, dramatically reducing cabin heat build-up — mirroring the real-world effect of cracking the windows.

Indoor temperature. The Indoors column estimates the temperature inside a building with windows closed and no air conditioning, simulating retained warmth, window solar gain, internal gains, and thermal mass hour by hour. You choose your building type from a dropdown — brick, modern insulated, Victorian terrace, stone cottage, timber frame, top-floor flat, or conservatory — and the physics model adjusts accordingly. Each type has its own insulation level, thermal mass, retained warmth, and glazing characteristics, so a stone cottage and a conservatory behave very differently on a hot day. The model now lags toward a realistic hourly target rather than repeatedly adding solar heat, so indoor temperatures typically peak 2–4 hours after the outdoor peak, which is why a house can still feel stifling at 10 pm on a summer day. Tick Managed alongside the dropdown to switch to the heatwave-advice model: curtains closed by day to cut solar gain, windows opened whenever outdoor air is cooler than inside.

Urban concrete surface temperature. Concrete and tarmac absorb far more solar energy than grass, and unlike grass they have no evaporative cooling. On a sunny summer afternoon, exposed paving can run 15–25 °C hotter than the surrounding air. SunScope models this using a surface energy balance approach that accounts for solar absorption, surface emissivity, and convective cooling by wind.

UV and sunburn. SunScope splits the solar UV spectrum into UV-A and UV-B components. The burn-time column estimates how long before you reach one Minimal Erythemal Dose (the clinical threshold for sunburn) based on the UV index and your Fitzpatrick skin type — selected from a dropdown in the column bar.

Soil temperature and moisture. Surface and 6 cm soil temperatures are shown for agricultural and outdoor-work planning. Soil moisture indicates whether the ground is workable or saturated — particularly useful for motorhome and caravan pitching.

Air quality, visibility, and pollen. Three atmospheric columns sit together after cloud cover in the table. Visibility shows horizontal visibility in kilometres, sourced from the CAMS model — values below 1 km indicate fog, below 10 km suggest mist or pollution haze. AQI shows the European Air Quality Index (0–100+), combining PM2.5, PM10, ozone, nitrogen dioxide, and sulphur dioxide, with colour-coded bands from Good to Hazardous. Pollen shows concentration in grains per cubic metre for a selectable pollen type — choose from total pollen, grass, birch, alder, mugwort, olive, or ragweed — with Low / Moderate / High / Very High labels. All three are sourced from the Copernicus CAMS air quality forecast.

The sky scope. The large circular visualisation at the top of the page shows the sky conditions for the currently selected hour. The sky colour smoothly interpolates through a full set of elevation-keyed gradients — from deep pre-dawn navy through golden sunrise, bright midday blue, warm sunset amber, and back to night — with a sun disc whose glow radius and intensity scale with the actual shortwave radiation at that moment. It refreshes automatically alongside the forecast.

Day strip weather and temperatures. Each day tab in the date selector shows the day's forecast at a glance: a weather icon representing the dominant daytime conditions (sun, cloud variants, or precipitation), plus the day's high and low SunSoak felt temperatures in warm and cool colours. The icon uses the actual daytime solar elevation and cloud category data so it reflects the real character of the day rather than a generic symbol.

Weather event banners and popups. When notable weather conditions are forecast — such as a frost, strong winds, fog, or a heat event — a banner appears above the forecast table with a brief alert. Tapping or clicking the event icon opens a detailed description popup explaining what the condition means and what to watch out for.

What's Coming — cosmic events almanac. A 🔭 panel below the forecast table shows upcoming astronomical events for your location over the next 90 days: meteor showers, lunar and solar eclipses, planetary conjunctions, and oppositions. Each entry shows the event name, peak date, a countdown, a short description, and a visibility note where the event is better from a particular hemisphere or location. When a cosmic event is currently active, it also appears as a banner above the forecast table alongside the weather alerts.

## What is SunSoak?

Standard UTCI is calculated assuming open, unshaded conditions with no precipitation — it tells you how the wind and sun affect your body, but not the full picture of where you actually are or what the weather is actively doing to you. SunSoak fills those gaps with three layers of original calculation stacked on top of the UTCI foundation.

The precipitation penalty. Rain and snow are not in UTCI. The soak-factor formula adds an original penalty based on rain intensity, snowfall rate, and wind speed — reflecting the extra chill of wet clothing and skin. Light drizzle (under 1 mm/hr) reduces the felt temperature by roughly 1–2 °C. Heavy rain combined with strong wind can push it down by 7–8 °C. Snowfall carries an additional penalty on top.

The environment modifier. UTCI assumes you are standing in the open. SunSoak adjusts the solar radiation load and air temperature for six distinct environments, selectable from a dropdown on the SunSoak column: Open / Exposed (the UTCI default); Forest / Woodland (canopy reduces direct radiation by ~85%, evapotranspiration cooling lowers apparent air temperature); High Altitude / Alpine (thinner atmosphere increases radiation dose by ~15% at 2,000 m); Beach / Lakeside (water and sand reflection increases effective solar load); River / Riverbank (partial canopy and strong evaporative cooling from the water surface); and Desert / Arid (extreme radiation from high-albedo ground, with significant ground-level heat adding to felt temperature). Selecting a Place or Activity profile automatically sets the most appropriate environment for that context — but you can always override it manually.

Mean radiant temperature. The full radiant heat load from surrounding surfaces — ground, walls, sky, and direct sun — is calculated as Mean Radiant Temperature (Tmrt) and fed into the UTCI polynomial. On a sunny day this alone can add 20–30 °C to the felt temperature compared to a shaded reading.

## Forecast profiles

SunScope organises its columns into profiles — curated sets of data tailored to different activities and use cases. Rather than showing every column at once, each profile surfaces the information that actually matters for that situation. You can switch between Basic, Home, and Vehicle using the buttons above the forecast table. Two dropdowns — Places and Activities — give access to a further set of tailored views. The Temps comparison and Custom column builder are part of SunScope Extra.

🌡️ Basic

The default view — clean and uncluttered, showing the essentials for any outdoor situation. Air temperature, wind speed, cloud cover, visibility, precipitation, and SunSoak — the felt-temperature index that combines sun, wind, humidity, rain, and your environment into a single honest number. The right starting point for most people most of the time.

🏠 Home

For managing indoor comfort without air conditioning. The indoor temperature column is central: select your building type from the dropdown (UK brick, modern insulated, Victorian terrace, stone cottage, timber frame, top-floor flat, or conservatory) and the physics model adjusts for that building's insulation, retained warmth, thermal mass, and glazing characteristics. Tick Managed to switch to the heatwave-advice model — curtains closed by day to block solar gain, windows opened whenever outdoor air is cooler than inside. Indoor temperatures typically peak 2–4 hours after the outdoor peak due to thermal mass, and the model reflects this lag for each building type. Supporting columns include air temperature, relative humidity and dew point (important for condensation and mould risk in cooler months), wind speed for ventilation decisions, cloud cover, air quality index and pollen (useful for allergy sufferers deciding whether to open windows), and precipitation — so you know whether to open the windows or bring the washing in.

🚗 Vehicle

Covers the parked and travelling vehicle experience — especially useful for anyone with children or pets, motorhome travellers, and caravan owners. The headline column is vehicle interior temperature: a physics-based estimate of how hot the cabin gets when parked and sealed, adjusted for your chosen vehicle type (car, MPV, SUV, motorhome, or caravan). Motorhomes and caravans are treated as insulated occupied living spaces, with reflective sandwich panels roughly 25–35 mm thick, less sun-exposed glass than a car, and retained warmth from previous hours, occupants, appliances, and background heating. Wind speed is included because it matters significantly for high-sided vehicles and caravans. Cloud cover and air temperature give context, precipitation covers driving conditions, and SunSoak tells you what it will feel like when you step outside. Soil moisture is included specifically for motorhome and caravan users — values above 40% indicate saturated ground where pitching or manoeuvring is likely to cause problems.

🌤️ Places

The Places dropdown gives access to seven location-specific views, each with its own tailored column set. Urban, Beach, Events, Park/Picnic, and Airport/Travel are free; Festival and Construction are part of SunScope Extra.

Urban — designed for anyone moving around a city on foot: commuting, shopping, sightseeing. The urban environment creates its own microclimate: buildings channel wind into gusts down narrow streets, concrete absorbs heat all day and radiates it back long after sunset, and the lack of vegetation means there's no evaporative cooling. Columns: air temperature, wind speed and direction, cloud cover, visibility, air quality index, UV-A index, burn time, SunSoak, precipitation, and concrete surface temperature.

Beach — UV exposure at the coast is significantly higher than inland: water reflects up to 25% of incoming UV back at you, and wet sand nearly as much. Both UV-A and UV-B are shown alongside burn time for your skin type. Dew point captures the humidity that makes hot beach days feel muggy, wind speed and direction matters for comfort and sea state, and sun elevation tells you when the UV load peaks. Visibility is included for sea-state and horizon conditions. SunSoak and precipitation round out the picture.

Events — for general outdoor gatherings: markets, sports fixtures, open-air concerts, and public events. Focuses on the crowd comfort picture: air temperature, wind speed and direction (useful for exposed grandstands and open sites), cloud cover, UV-A and burn time for daytime events, SunSoak for overall felt comfort, precipitation, pollen (important for allergy-sensitive attendees), and concrete surface temperature — relevant for anyone standing or sitting on sun-exposed hard standing for extended periods.

Park / Picnic — a lighter view for casual outdoor time in green spaces. Shows the essentials without the urban or specialist columns: air temperature, wind speed, cloud cover, burn time, SunSoak, precipitation, and pollen — useful for anyone with hay fever deciding whether to head out.

Airport / Travel — focused on the conditions that affect journeys rather than outdoor comfort. Shows air temperature, wind speed and direction (relevant for delays and turbulence at exposed airports), cloud cover, visibility (critical for flight operations and driving to the terminal), and precipitation.

Festival · Extra — multi-day outdoor events live or die by two things: the weather comfort and the state of the ground. Focuses on SunSoak for how cold and wet conditions will actually feel, wind speed and direction for tent and stage exposure, dew point for overnight condensation, UV-A and burn time for daytime sun protection, precipitation for planning, air quality index and pollen — particularly relevant for multi-day outdoor exposure — and soil moisture — the mud indicator. Values above 40% mean the ground is saturated and vehicle access, camping areas, and walkways will be affected.

Construction · Extra — for site managers and outdoor workers. Safety and productivity on a construction site depend on conditions at ground level and in the air. Shows air temperature, wind speed and direction (critical for working at height and crane operations), cloud cover, visibility, air quality index (dust and diesel particulates compound background pollution), UTCI for heat stress on workers, SunSoak for wet-weather comfort, and precipitation.

🎯 Activities

The Activities dropdown organises views by what you are actually doing outdoors. Farming, Cycling, Running, and Dog Walking are free; Sailing, Winter Sports, Naturist, Hiking, Photography, and Fishing are part of SunScope Extra.

Farming — built for organic growers first, but just as useful for any farmer, smallholder, or market gardener working the land. Decision-making on the land is driven by conditions at ground level, not just the air. Shows air temperature, relative humidity and dew point (critical for frost risk and disease pressure on crops), wind speed and direction (essential for safe windows to apply foliar feeds and organic-approved sprays without drift onto buffer zones or watercourses), cloud cover and sun elevation for light levels, SunSoak for heat stress on the person working outdoors, precipitation, air quality index and pollen (relevant for outdoor workers and foliar-feed timing), and the three soil columns: surface soil temperature, soil temperature at 6 cm (the root zone for most seedlings), and soil moisture — so you know whether the ground is workable or waterlogged before you head out.

Cycling — tailored for road and trail cyclists. Wind is the dominant factor: headwinds add significant effort, crosswinds affect handling, and gusts are a safety concern on open roads. Shows air temperature, wind speed and direction, cloud cover, burn time, SunSoak, precipitation, and visibility — useful for road cycling in low-light or foggy conditions.

Running — for outdoor runners monitoring heat stress and air quality. Shows air temperature, relative humidity (sweat evaporation is less effective in humid air, raising heat stress faster), wind speed, cloud cover, UTCI for raw heat stress, burn time, SunSoak, precipitation, and pollen — relevant for asthma and hay fever sufferers pacing their outdoor training.

Dog Walking — focused on the comfort and safety of both owner and dog. Shows air temperature, wind speed, cloud cover, SunSoak, precipitation, and pollen. The Vehicle profile's concrete surface temperature is the better companion for pavement heat safety on hot days.

Sailing · Extra — conditions out at sea can be dramatically different from what the shore feels like. Leads with air temperature (hypothermia is a real risk — water conducts heat away from the body twenty-five times faster than air), dew point (condensation on sails and equipment is a practical concern at dawn and dusk), wind speed with gusts, wind direction, cloud cover, and sun elevation for visibility and glare. UV exposure is significantly higher on open water due to reflection off the surface, so UV-A index and burn time are included. SunSoak captures the combined effect of wet, windy conditions, visibility (essential for safe passage — fog and haze at sea are serious hazards), and precipitation rounds out the picture for passage planning.

Winter Sports · Extra — for skiers, snowboarders, and mountain walkers. UV intensity increases by roughly 10% for every 1,000 m of altitude, and snow reflects up to 80% of UV back upward — making mountain environments one of the highest-risk UV exposures outside a solarium. Both UV-A and UV-B are shown with burn time. Wind speed and direction is critical for wind chill at speed and for avalanche and exposure risk on open slopes. Sun elevation indicates glare and visibility conditions on snow. SunSoak, air temperature, cloud cover, visibility (critical for whiteout and low-cloud conditions on the mountain), and precipitation (snow vs rain) complete the picture.

Naturist · Extra — with no clothing buffer between skin and environment, every weather variable matters more. Wind chill at even modest speeds becomes significant, so both the raw UTCI and SunSoak are shown. Both UV-A and UV-B are included — full-body UV exposure is a serious consideration — alongside burn time, sun elevation, dew point for humidity comfort, wind, cloud cover, air quality index, pollen, and precipitation.

Hiking · Extra — for hillwalkers and long-distance trail users. Conditions in upland and remote terrain can shift rapidly and the consequences of being caught out are more serious than in urban areas. Shows air temperature, wind speed and direction, cloud cover, sun elevation, both UV-A and UV-B with burn time (altitude increases UV exposure), UTCI and SunSoak, precipitation, and visibility (critical for navigation in poor conditions).

Photography · Extra — for outdoor and landscape photographers who need to understand light quality, cloud diffusion, and solar position. Shows air temperature, cloud cover, sun elevation, direct radiation and diffuse radiation (the ratio of these two values determines whether light is harsh or soft), visibility (haze and atmospheric clarity), and precipitation.

Fishing · Extra — river and sea anglers need to read conditions that most weather apps don't surface. Shows air temperature, dew point (morning condensation and hatch activity on rivers), wind speed and direction, cloud cover, SunSoak for what it will actually feel like on an exposed bank or boat, precipitation, and visibility for sea and estuary conditions.

🌡️ Temps · Extra

A comparison view that brings all temperature-derived columns into one place: air temperature, SunSoak felt temperature, surface soil temperature, concrete surface temperature, vehicle interior temperature, indoor temperature, and managed indoor temperature. Useful for understanding how the same weather conditions manifest across different environments simultaneously.

⚙️ Custom · Extra

Full control over which columns appear in the table. Toggle any combination of air temperature, dew point, relative humidity, wind, direction, cloud, visibility, air quality index, pollen, sun elevation, direct and diffuse radiation, mean radiant temperature, UTCI delta, UTCI, UV-A, UV-B, burn time, vehicle interior, indoor, managed indoor, soil temperatures, soil moisture, concrete surface, precipitation, and SunSoak. Build exactly the view that suits your situation.

## Column reference

Every column in the SunScope forecast table is described below.

Column | What it shows
--- | ---
Air °C | Standard air temperature at 2 m above ground — the thermometer reading. Does not account for sun, wind, or humidity.
RH % | Relative humidity: how much moisture the air holds as a percentage of its maximum capacity at that temperature. High RH makes warm days feel stickier and cold days feel rawer.
Dew Point | The temperature at which air becomes saturated and moisture begins to condense. Above 16 °C it starts to feel muggy; above 21 °C it feels oppressive. A better measure of absolute humidity than RH.
Wind | Mean wind speed at 10 m, with peak gust in brackets where significantly higher. Wind is the primary driver of wind chill — a key ingredient in the UTCI calculation.
Dir | The compass direction the wind is blowing from, shown as an arrow and abbreviated label. Useful for route planning and spray timing.
Cloud | Total cloud cover as a percentage of sky. High cloud blocks solar radiation, reducing daytime heating and UV exposure.
Visibility km | Horizontal visibility in kilometres, sourced from the Copernicus CAMS air quality model. Below 1 km indicates fog or very thick haze; below 10 km suggests mist, smoke, or significant pollution. Relevant for driving, flying, cycling, and photography.
AQI | European Air Quality Index (0–100+), combining PM2.5, PM10, ozone, nitrogen dioxide, and sulphur dioxide. 0–20 = Good; 20–40 = Fair; 40–60 = Moderate; 60–80 = Poor; 80–100 = Very Poor; 100+ = Hazardous. Sourced from Copernicus CAMS.
Pollen | Pollen concentration in grains per cubic metre for the selected pollen type — choose from total, grass, birch, alder, mugwort, olive, or ragweed via the dropdown. Sourced from the Copernicus CAMS pollen forecast. Low = <10; Moderate = 10–50; High = 50–200; Very High = 200+.
Sun ° | The angle of the sun above the horizon in degrees. Below 0° the sun has set. The higher the elevation, the more intense the radiation reaching the ground.
Direct W/m² | Shortwave solar radiation arriving as a direct beam from the sun. The primary driver of skin heating on sunny days.
Diffuse W/m² | Solar radiation scattered from all directions across the sky. Present even under cloud cover; contributes to the overall solar heat load.
Tmrt °C | Mean Radiant Temperature — the temperature your skin effectively "sees" from all surrounding surfaces and the sun combined. Can exceed air temperature by 20–30 °C on a sunny day; this is why shade feels so much cooler.
UTCI−Air Δ | The gap between the UTCI felt temperature and the plain air temperature. A large positive value means solar radiation is adding significant heat stress beyond what the thermometer shows.
UTCI °C | Universal Thermal Climate Index — the raw felt temperature combining air temp, humidity, wind, and solar radiation. Does not include precipitation effects.
UV-A | Estimated UV-A radiation index. UV-A penetrates deeper into the skin and contributes to long-term ageing and some skin cancers, even through glass. Present throughout daylight hours.
UV-B | Estimated UV-B radiation index. Causes sunburn and drives vitamin D production. Intensity falls sharply at low solar elevations due to the longer atmospheric path length.
Burn time | Estimated time to reach one Minimal Erythemal Dose (MED) — the threshold for sunburn — based on the UV index and your selected Fitzpatrick skin type. A guide, not a medical measurement.

SunSoak °C

SunScope's signature felt-temperature index. Starts from UTCI then adds three layers: a rain and snow penalty (wet clothing can drop felt temperature by up to 8 °C), an environment modifier for where you actually are (forest, alpine, beach, river, desert), and full mean radiant temperature from surrounding surfaces. The most honest single answer to: what will it actually feel like out there?

Precip mm | Expected rainfall or snowfall in mm per hour. Even light drizzle meaningfully reduces felt temperature when combined with wind.
Soil °C surface | Temperature of the soil at the surface (0 cm depth). Most seeds germinate above 7–10 °C. Useful for sowing decisions and frost assessment.
Soil °C 6 cm | Soil temperature at 6 cm depth — the root zone for many crops and seedlings. Lags behind the surface by several hours.
Soil moisture | Water saturation of the top 1 cm of soil as a percentage. Above 40% indicates saturated ground; below 20% is dry. Useful for assessing whether ground is workable, and for motorhome or caravan pitch suitability.
Concrete °C | Estimated temperature of sun-exposed urban paving. Concrete absorbs more solar energy than grass and cannot cool itself through evaporation — surface temps can run 15–25 °C above air temperature on sunny days.
Vehicle °C | Estimated ambient cabin temperature inside a sealed, parked vehicle — adjusted for your chosen vehicle type. Values above 35 °C are dangerous for children and pets; above 45 °C potentially fatal within minutes.

Indoors °C

Estimated temperature inside a building with windows closed and no active cooling. Select your building type from the dropdown — brick, modern insulated, Victorian terrace, stone cottage, timber frame, top-floor flat, or conservatory. Each type has its own insulation, retained warmth, thermal mass, and glazing characteristics. Indoor peak typically lags the outdoor peak by 2–4 hours due to thermal mass.

Managed °C | The same building model with two interventions applied: curtains closed by day to block solar gain, and windows opened whenever outdoor air is cooler than inside. Toggle with the Managed tick next to the building dropdown. Shows how much passive cooling can reduce indoor heat compared to doing nothing.

## Urban heat: concrete surface temperature

The UTCI standard was developed with a natural grass surface as its reference ground — the assumption being that you're standing in a park or open field. In a city, that assumption breaks down. Concrete and tarmac absorb more solar energy than grass, and unlike grass they cannot cool themselves through evaporation. On a sunny summer afternoon, exposed concrete can run 15–25 °C hotter than the surrounding air.

SunScope's Concrete surface column estimates the temperature of sun-exposed urban paving using an energy-balance model that accounts for how much solar radiation the surface absorbs, how efficiently the air above it carries that heat away (which depends on wind speed), and the reflective properties of typical urban concrete. The result gives you a sense of the contact heat stress you'd experience sitting, standing, or walking barefoot on city surfaces — something the standard UTCI value alone won't tell you.

The column is enabled by default in the Places → Urban variant and colour-coded: values above 30 °C are shown in amber, above 40 °C in red.

## Vehicle interior temperature

A sealed, parked vehicle heats up far faster than most people expect. SunScope's Vehicle column models the ambient cabin air temperature experienced by an occupant who is seated out of direct sunlight — the classic scenario of a child or pet left inside a parked car.

The calculation combines two physical processes. The first is body panel conduction: body panels absorb solar radiation and conduct heat into the cabin regardless of the sun's position in the sky. Thin metal car panels pass much more of this heat through than the insulated sandwich panels used in many motorhomes and caravans. This is the slow, relentless background heat that builds even on overcast days. The second is side-window solar gain: when the sun is at an elevation where its rays cut through the side glass rather than striking the roof or reflecting off at a shallow angle, additional heat enters the cabin. Because the occupant is modelled as sitting out of the direct beam, this energy goes into raising the ambient cabin air temperature rather than heating the person directly — which is precisely what makes it so dangerous. The air around you heats up steadily while you remain unaware of how hot the environment has become.

Wind speed has almost no effect on a sealed vehicle and is not factored in unless the Ventilation toggle is enabled. For cars, the figure represents the cabin temperature after roughly 45–60 minutes of parking. For motorhomes and caravans, the model allows for lower heat gain, slower response from insulated panels, and retained occupied-space warmth, so the estimate stays much closer to the real living-space temperature on cool or moderate sunny days. Values above 35 °C are shown in amber (dangerous for children and pets); above 45 °C in red (potentially fatal within minutes).

## Reading the stress bands

SunScope maps every SunSoak value to a thermal stress band so you can read conditions at a glance:

UTCI range | Band | What it means outdoors
--- | --- | ---
Below −27 °C | Polar | Survivable only with expedition-grade kit; do not go outside unprepared
−27 to −13 °C | Arctic | Very strong cold stress; full winter protection needed
−13 to 0 °C | Freezing | Strong cold stress; warm layers essential
0 to 9 °C | Cold | Moderate cold stress; coat and gloves advised
9 to 18 °C | Chilled | Slight cold stress; comfortable with a light jacket
18 to 26 °C | Comfortable | No thermal stress; ideal outdoor conditions
26 to 32 °C | Mod heat | Moderate heat stress; stay hydrated
32 to 38 °C | Strong heat | Strong heat stress; limit strenuous activity
38 to 46 °C | V. strong heat | Very strong heat stress; seek shade and cool fluids
Above 46 °C | Extreme heat | Extreme heat stress; dangerous for outdoor exposure

## Frequently asked questions

Got a specific question — about UTCI, the SunSoak index, UV and sunburn times, how hot a parked car or pavement really gets, keeping your home cool without air conditioning, air quality, pollen, or soil and farming data? Our dedicated FAQ page answers the most common questions in plain language, grouped by topic.

## Get in touch

SunScope is an independent project. If you have feedback, spotted a bug, or are interested in using SunScope data for your business or website, feel free to reach out via hello@sunscope.net.