# Frequently Asked Questions

See the sun the way your skin does.

## Understanding SunScope

What is UTCI and why is it more accurate than feels-like temperature?

UTCI stands for Universal Thermal Climate Index. Unlike a standard feels-like temperature - which usually only adjusts for wind chill or humidity on their own - UTCI uses a full physiological model of the human body. It combines four factors at once: air temperature, humidity, wind speed, and the heat from solar radiation hitting your skin directly.
That last one is huge. On a sunny day the sun can make you feel 10-15 degrees warmer than the air temperature alone, and most weather apps ignore this entirely. UTCI is a peer-reviewed scientific standard used in public health systems and heat-health warning services across Europe. SunScope uses it because it is the most honest number available for describing how weather actually feels on your body.

What is SunSoak and how is it different from UTCI?

UTCI is the scientific foundation — a peer-reviewed biometeorological standard that combines air temperature, humidity, wind, and solar radiation. But it has gaps. It assumes you are standing in open conditions with no precipitation. SunSoak is SunScope's extended index that fills those gaps with three extra layers.
First, a rain and snow penalty: the extra chill of wet clothing and skin is not in UTCI. Light drizzle drops felt temperature by 1-2 degrees; heavy rain combined with strong wind can push it down 7-8 degrees. Second, an environment modifier: SunSoak adjusts the solar and thermal load for where you actually are — forest canopy, alpine altitude, beach or lakeside glare, shaded riverbank, or desert ground heat. Switch it in the SunSoak column dropdown to match your surroundings. Third, full mean radiant temperature from all surrounding surfaces, not just the direct sun beam.
On a dry day in the open, SunSoak and UTCI will be close. In rain, in a forest, at altitude, or by the sea they can differ significantly — which is exactly what your body experiences.

What is the difference between UTCI and heat index?

Heat index is a simple table-based formula that adjusts air temperature for humidity only. It was designed for shade conditions and ignores wind and solar radiation entirely. UTCI is a full physiological model accounting for air temperature, humidity, wind speed, and mean radiant temperature from solar radiation and surrounding surfaces.
In sunny or windy conditions the two values can differ by 10-20 degrees. UTCI is the standard used in European heat-health warning systems and urban heat research. Heat index is a rough guide; UTCI is what your body actually experiences.

Why does SunScope sometimes show a much higher temperature than my regular weather app?

On clear sunny days, direct solar radiation heats your skin significantly - sometimes adding 10 degrees or more to what the air temperature alone would suggest. SunScope calculates mean radiant temperature from real shortwave radiation forecast data, capturing this solar heat load. Standard weather apps report air temperature or a basic wind-chill formula and ignore solar radiation entirely.
On a still, cloudless 18 degree day in June, SunScope might show a felt temperature of 28 degrees. That is not an error - that is what your skin actually experiences standing in direct sun.

Why does SunScope sometimes show a lower temperature than my regular weather app?

Wind chill and precipitation both reduce felt temperature. If it is raining or blustery, the SunSoak value will be noticeably lower than the thermometer reading - which is exactly what your body experiences. A 15 degree day with heavy rain and a strong wind can feel closer to 8 or 9 degrees in real terms. Most apps report only the air temperature; SunSoak captures the full picture.

## Reading the Forecast

How do I read the SunScope table?

Each row in the table is one hour of the day, with the time shown in the first column. The most important column is SunSoak - SunScope's felt-temperature index combining air temperature, humidity, wind, solar radiation, rain, and your environment into a single honest number.
Colour coding tells you how comfortable each hour will be at a glance: blue shades mean cold, green means comfortable, yellow and orange mean warm or hot, and red means dangerous heat stress. Use the SunSoak column dropdown to set your environment - Forest, Alpine, Beach, River, or Desert - and the values will adjust accordingly. Other columns show vehicle cabin temperature, indoor building temperature, UV index, burn time, concrete surface temperature, soil data, air quality, and pollen. Switch between profiles using the buttons and dropdowns above the table - Basic, Home, Vehicle, then the Places and Activities dropdowns for location and activity-specific views. Hover any column header for a plain-language description of what it shows.

What do the different profiles and dropdowns show?

Each profile is a curated set of columns relevant to a different activity or situation.
Basic shows the core weather picture: felt temperature, sky conditions, wind, and precipitation.
Home adds indoor building temperature for your selected building type, humidity, and dew point.
Vehicle adds car or motorhome cabin temperature, soil moisture for pitch assessment, and visibility.
The Places dropdown offers Urban, Beach, Events, Park/Picnic, and Airport/Travel (all free), plus Festival and Construction (Extra). The Activities dropdown includes Farming, Cycling, Running, and Dog Walking (free), plus Sailing, Winter Sports, Naturist, Hiking, Photography, and Fishing (Extra).
SunScope Extra also unlocks Temps (a side-by-side temperature comparison) and Custom, which lets you build a fully custom column layout.

What does the weather icon and temperature on each day tab mean?

Each day tab in the date strip shows a small weather icon representing the dominant daytime sky conditions - a sun disc for clear days, cloud variants for cloudy days, or a precipitation icon for rainy or snowy days. Below the icon are the day high and low SunSoak felt temperatures shown in warm and cool colours.
The icon is derived from actual daytime solar elevation and cloud data, so it reflects the real character of the day rather than a generic symbol picked from a fixed set.

What are the weather event banners above the forecast table?

When notable weather conditions are forecast - such as a ground frost, strong wind warning, fog, or a heat event - a coloured banner with a brief alert appears above the table. Tapping or clicking the event icon opens a popup with more detail about what the condition means and what to watch out for. Multiple events can appear at once if conditions warrant it.

Why does the sky display show the wrong time of day?

The sky scope always shows current conditions - it reflects the actual time right now, not the hour you are browsing in the table. The sun position, sky colour, and glow intensity are all calculated from the real solar elevation and radiation data for the current moment.
If you are looking at a future or past hour in the forecast table, the sky display does not follow - it stays locked to now by design. It is a live view of the current sky, not a preview of a future one.

How do I set or change my location?

Use the search bar at the top of the forecast page. Type any city, town, village, or postcode and select from the dropdown results. SunScope uses the Open-Meteo geocoding API so it works for locations worldwide, not just the UK. Your last searched location is remembered automatically the next time you visit.

## Sun and UV

What UV level is dangerous?

The World Health Organisation UV index scale:
1-2 (Low) - No protection needed for short exposure.
3-5 (Moderate) - Wear sunscreen and a hat for exposure over 30 minutes.
6-7 (High) - Seek shade during midday, apply SPF 30 or above.
8-10 (Very High) - Minimise direct sun between 11am and 3pm.
11+ (Extreme) - Avoid outdoor exposure during peak hours entirely.
In the UK, UV 6 or above is common on clear summer days between May and August. In southern Europe or at altitude it regularly reaches 9 or 10. SunScope shows the UV index for every hour so you can see exactly when protection is needed and when the risk drops off in the evening.

How long until I get sunburn today?

It depends on two things: the current UV index and your skin type. SunScope shows a Burn time column estimating how many minutes you can spend in direct unshaded sun before reaching the threshold for sunburn - known as one Minimal Erythemal Dose (MED). You set your Fitzpatrick skin type in the settings and the column updates accordingly.
As a rough guide: at UV 8 or above, fair skin (type I or II) can start to burn in under 10 minutes. Medium skin types have around 20-25 minutes. Darker skin types have more natural protection but are not immune. The burn time assumes no sunscreen and no shade. Apply factor 30 or above if you will be outside for longer than your estimated window.

What is the difference between UV-A and UV-B?

UV-A has a longer wavelength and penetrates deeper into the skin. It is present throughout all daylight hours, passes through glass, and is the primary cause of long-term skin ageing and contributes to some skin cancers. UV-B has a shorter wavelength, causes sunburn directly, and drives vitamin D production.
UV-B intensity is much more angle-dependent: strongest when the sun is high and falling sharply in early morning and late afternoon due to the longer atmospheric path the radiation must travel. SunScope shows both indices separately so you can make informed decisions about both immediate burn risk and long-term UV exposure.

How does shade affect how hot I feel?

On a sunny day shade can make a very significant difference - often 8 to 12 degrees in UTCI terms - because it removes the direct solar radiation load entirely. However shade does not reduce the air temperature or humidity, so on very humid days you will still feel uncomfortably warm even in full shade.
SunScope shows the UTCI value for open sun exposure. If you are planning to stay in shade, the felt temperature you actually experience will be noticeably lower than the figure shown.

## Heat, Vehicles and the Urban Environment

How hot does a car get in the sun?

Frighteningly hot, and faster than most people expect. On a mild 20 degree day with strong sunshine, the inside of a sealed car can reach 40-45 degrees within 20 minutes and 50 degrees or more within an hour. On a hot 30 degree day it can hit 60 degrees. The glass acts like a greenhouse, letting solar radiation in but trapping the heat inside.
SunScope calculates cabin temperature hour by hour using the actual solar radiation forecast for your location. Anything above 35 degrees is dangerous for a child or pet left inside. Above 45 degrees can be fatal within minutes. Always check the Vehicle column before leaving anyone in a parked car.

Does opening car windows reduce the temperature inside?

Yes, significantly. Open windows allow convective airflow to flush hot cabin air out continuously, reducing heat build-up by roughly 60-80% compared to a sealed vehicle. SunScope Vehicle column has a Ventilation toggle that switches the physics model to a ventilated state, showing the estimated cabin temperature with windows open alongside the sealed figure so you can compare both directly.

Is it safe to leave a dog in a parked car?

No. On any warm or sunny day - even with cloud cover - a sealed vehicle heats up rapidly to temperatures that can cause heatstroke and death in animals within minutes. Dogs cannot cool themselves as efficiently as humans and are at risk at cabin temperatures above 32 degrees.
SunScope Vehicle interior column gives an hour-by-hour estimate of cabin temperature. If the forecast shows values in amber (above 35 degrees) or red (above 45 degrees), the vehicle is not safe for a dog, cat, or young child, even for a few minutes. In the UK it is also a criminal offence to leave an animal in a vehicle in conditions likely to cause suffering.

How hot does pavement or concrete get in summer?

Exposed concrete and tarmac can be 15-25 degrees hotter than the surrounding air on a sunny day. Unlike grass they have no evaporative cooling, and their dark colour means they absorb a large fraction of incoming solar radiation. They also radiate that heat back upward, making urban areas feel significantly warmer than open countryside - known as the urban heat island effect.
The rule of thumb: if you cannot hold your hand on the surface for 7 seconds it is too hot for dog paw pads. SunScope Concrete surface column estimates pavement temperature using an energy-balance model driven by the real solar radiation forecast.

Is it safe to run outside today?

SunScope gives you three numbers that together answer this.
Check UTCI: below 26 degrees is comfortable for running, 26-32 is warm so hydrate well and slow your pace, above 32 is heat stress and you should move your run to early morning or evening instead.
Check AQI: if it is 4 or 5, outdoor exercise significantly increases the amount of pollutants your lungs absorb - consider moving indoors on those days.
Check UV: if the index is 6 or above and you will be out during midday, apply sunscreen and cover exposed skin.
Early morning usually gives comfortable temperatures, low UV, and good air quality all at once - the sweet spot for outdoor exercise.

## Your Home

How do I keep my house cool in a heatwave without air conditioning?

The standard approach is to keep curtains and blinds closed during the day to block direct solar gain through windows, then open windows once the outdoor air temperature drops below the indoor temperature - usually in the evening or early morning. SunScope Home profile lets you select your building type so the model reflects how your building actually heats up and retains heat. Ticking Managed shows what you could achieve by following this advice hour by hour - so you can see exactly when to open up for maximum benefit.

Why is my house hotter in the evening than during the day?

Building materials absorb heat slowly throughout the day and release it gradually over several hours - a property called thermal mass. A solid stone cottage or Victorian terrace has very high thermal mass and can stay warm well into the night, while a timber frame new build or conservatory responds almost immediately to outdoor temperature changes.
SunScope building type selector lets you match the model to your actual home, so the indoor temperature lag it shows reflects your building rather than a generic average.

What is thermal mass and why does it matter?

Thermal mass is the ability of a material to absorb, store, and slowly release heat. Heavy materials like stone, brick, and concrete have high thermal mass - they warm up slowly during the day but also release that heat slowly overnight, keeping rooms warmer later into the night. Lightweight materials like timber and glass have low thermal mass and respond quickly to temperature changes.
This is why a stone cottage stays cool during a hot day but can feel stuffy at midnight, while a modern timber-frame house heats up and cools down much faster. SunScope Home profile uses the thermal mass of your selected building type to model indoor temperature across the full day and into the following morning.

## Air Quality and Pollen

What does an air quality index of 3 mean?

SunScope uses the European Air Quality Index, which runs from 1 (Very Good) to 5 (Very Poor). An AQI of 3 means Moderate. For most healthy people this is fine - you can go about your day normally.
But if you have asthma, a heart condition, or a respiratory illness, or if you are elderly or very young, you may start to notice some effects at this level - a slight tightening of the chest, irritated eyes, or fatigue during exercise. At AQI 4 (Poor) everyone should reduce prolonged outdoor exercise and sensitive groups should avoid it entirely. At AQI 5 (Very Poor) even healthy people should limit time outside. The AQI in SunScope combines five pollutants: PM2.5, PM10, ozone, nitrogen dioxide, and sulphur dioxide.

What is the difference between PM2.5 and PM10?

PM stands for particulate matter - tiny particles suspended in the air. PM10 refers to particles up to 10 micrometres in diameter, which includes dust, pollen, and mould spores. PM2.5 refers to much finer particles up to 2.5 micrometres, including combustion particles from vehicle exhausts and wood burning.
PM2.5 is the more dangerous of the two because the particles are small enough to penetrate deep into the lungs and enter the bloodstream. On high-pollution days PM2.5 is usually the dominant driver of the AQI value shown in SunScope.

What does the pollen count mean for hay fever sufferers?

SunScope shows pollen in grains per cubic metre of air:
Below 10 - Low. Most people will not notice symptoms.
10-30 - Moderate. Sensitive sufferers may get mild symptoms.
30-80 - High. Most hay fever sufferers will have symptoms.
Above 80 - Very High. Symptoms likely even with antihistamines.
Choose the right pollen type for you - SunScope lets you pick from grass, birch, alder, mugwort, olive, ragweed, or total pollen, so you see only the count relevant to your allergy. In the UK grass peaks June to August. Birch and alder peak in spring. Pollen counts are often lower after rain and in the evenings.

What does visibility mean in the forecast?

Visibility in SunScope is horizontal visibility in kilometres - the distance at which you could clearly see a known object. As a guide:
Below 1 km - Dense fog. Dangerous for driving.
1-4 km - Fog or thick mist.
4-10 km - Hazy but manageable.
Above 10 km - Good visibility.
Visibility drops sharply in fog, heavy rain, snow, dust events, and high-pollution days. It is sourced from the Copernicus CAMS forecast via Open-Meteo.

## Farming and Outdoors

What does dew point mean and why does it matter?

The dew point is the temperature at which air becomes saturated with moisture and water starts to condense. When the outdoor air temperature falls to the dew point, fog forms and surfaces become wet with dew or frost.
For organic growers this is critical - applying foliar feeds or organic sprays when the temperature is near the dew point risks poor uptake and possible leaf scorch. For caravanners a high dew point overnight means wet awnings and condensation in the morning. A dew point above 18 degrees feels oppressively humid even if the air temperature is not extreme, because sweat cannot evaporate efficiently.

What is the difference between a ground frost and an air frost?

An air frost is when the official air temperature measured 1.2 metres above the ground falls below 0 degrees. A ground frost is when the temperature at or just above the surface falls below 0 degrees - which can happen even when the air temperature is 2 or 3 degrees, because the ground radiates heat upward on clear still nights and chills faster than the air above it.
Ground frosts are what damage tender plants, ice over car windscreens, and make paths slippery. They can catch you out on nights when the weather app says above zero. SunScope flags frost events in the weather event banners above the table.

When is it safe to spray crops or apply foliar feeds?

Whether you are applying an organic foliar feed, a compost tea, or a permitted copper or sulphur treatment, safe spraying requires low wind speeds - typically below 3 metres per second - to prevent drift onto neighbouring land, watercourses, or buffer zones, which matters for maintaining organic certification. Cooler temperatures reduce evaporation and the risk of leaf scorch, and spraying in the evening protects foraging bees and other beneficial insects. You want no rain forecast for several hours so the product is not washed off before it can work, and the temperature comfortably above the dew point to avoid condensation interfering with coverage.
SunScope Farming profile shows wind speed and direction, air temperature, relative humidity, dew point, and precipitation all in one view - so you have every variable you need without switching between multiple apps.

What soil temperature do seeds need to germinate?

Most vegetable seeds need soil temperatures above 7-10 degrees to germinate reliably. Warm-season crops like courgettes, beans, and sweetcorn need 12-15 degrees or more. Cool-season crops like lettuce and spinach can germinate at 4-5 degrees. Sowing too early into cold soil leads to seeds rotting before they sprout.
SunScope shows both surface soil temperature and the 6 cm depth temperature - the root zone where germination actually happens. The 6 cm figure lags behind the surface by several hours and gives a more realistic picture of what seeds in the ground are actually experiencing.

How can I tell if the ground is too wet for a motorhome or caravan?

SunScope soil moisture column shows the volumetric water content of the top centimetre of soil in cubic metres per cubic metre. As a guide:
Above 0.4 - Saturated. A heavy vehicle is likely to sink or churn the surface.
0.3-0.4 - Damp but borderline. Proceed with caution.
Below 0.3 - Usually firm enough for most vehicles.
Below 0.2 - Dry and solid.
The Vehicle profile includes soil moisture by default for motorhome and caravan users assessing pitch suitability before arriving on site.

## About SunScope

Does SunScope show air quality and pollen forecasts?

Yes. Three air environment columns sit after Cloud cover in the table: Visibility (horizontal visibility in km, useful for fog, haze, and driving conditions), AQI (the European Air Quality Index combining PM2.5, PM10, ozone, nitrogen dioxide, and sulphur dioxide), and Pollen (concentration in grains per cubic metre with a type picker for grass, birch, alder, mugwort, olive, ragweed, or total). All three are sourced from the Copernicus CAMS forecast via Open-Meteo. Toggle them using the column buttons above the table.

How far ahead does the forecast go?

The free tier shows 3 days of hourly data. SunScope Extra unlocks 14 days. The forecast auto-refreshes every 5 minutes while the page is open, so the current hour always reflects the latest available data from Open-Meteo. You do not need to manually reload the page to get the freshest figures.

How accurate is SunScope?

SunScope uses Open-Meteo forecast data sourced from ECMWF and national meteorological services - the same underlying models used by professional forecasters. The UTCI calculation follows the peer-reviewed Bröde 2012 polynomial exactly.
The derived columns - vehicle temperature, indoor temperature, concrete surface - are physics-based estimates rather than measured values, and will vary based on local factors like building construction, shading, surface colour, and vegetation. Treat them as well-informed estimates rather than precise measurements. They are consistently closer to reality than ignoring these effects entirely.

Is SunScope free?

The core forecast is free for any location worldwide with no account required. Free includes Basic, Home, Vehicle, the Places variants Urban, Beach, Events, Park/Picnic, and Airport/Travel, and the Activities variants Farming, Cycling, Running, and Dog Walking.
SunScope Extra (2 pounds per month) unlocks 14-day forecasts, the specialist Places variants Festival and Construction, the specialist Activities variants Sailing, Winter Sports, Naturist, Hiking, Photography, and Fishing, the Temps comparison profile, and Custom column control where you choose exactly which columns appear and in what order.

Is there a SunScope mobile app?

SunScope is a web app that works on any device through your browser - no installation required. On a smartphone you can add it to your home screen for a near-native app experience.
On iPhone: open SunScope in Safari, tap the Share button, then select Add to Home Screen.
On Android: open in Chrome, tap the three-dot menu, then Add to Home Screen.
It will appear as an icon on your phone just like a regular app and opens directly to the forecast without a browser address bar.

What data sources does SunScope use?

Forecast data comes from Open-Meteo, which aggregates ECMWF, GFS, and national meteorological service models. The UTCI calculation follows the Bröde et al. 2012 polynomial. Air quality, visibility, and pollen data are sourced from the Open-Meteo Air Quality API, which draws on the Copernicus CAMS forecast. Geolocation search uses the Open-Meteo geocoding API.

Does SunScope work outside the UK?

Yes - SunScope works for any location worldwide. Search for any city, town, or village using the search bar. The indoor temperature model offers seven building types - brick, modern insulated, Victorian terrace, stone cottage, timber frame, top-floor flat, and conservatory - so you can pick the one that best matches your building wherever you are. All other columns (UTCI, vehicle, UV, soil, concrete) are fully location-agnostic.

For the science and methodology behind every column, see the About page. To check current conditions for your location, go to the Forecast. Questions not answered here? Email hello@sunscope.net.