Solvora - UV Index & Sun Timer
Solvora answers two questions before you head outside: how strong is the sun's ultraviolet light right now, and how long have I already been out in it? It shows the current UV index for your location, or for a place you search by name, together with an hourly forecast for today and tomorrow and the time the data was fetched.
When you go out, start the sun timer. It works out your elapsed time from the moment you pressed start, so a reload or a background tab does not lose any minutes. From the hourly forecast, your skin type and any sunscreen you log, it estimates the UV dose you have collected and the suggested time at which reddening may begin. A separate card tracks when you last applied sunscreen and when it is due again.
If UV data cannot be loaded, Solvora says so instead of showing a misleading 0. Sessions, settings and sunscreen entries are kept only in this browser, with no account.
The app runs entirely in your browser. What you enter is saved only on this device.
How to use Solvora
- Pick your skin type. On first use, choose the Fitzpatrick skin type (I to VI) closest to yours. It sets how much UV the app treats as your reddening threshold. You can change it later in Settings.
- Allow location or choose a place. The UV tab asks the browser for your location. If you would rather not share it, or it fails, tap Choose a place and search for a city. Use my location switches back.
- Read the UV index and forecast. The gauge shows the current value with its WHO band and a short tip. Below it, switch between Today and Tomorrow to see the hourly forecast chart.
- Start the sun timer. Tap Start a sun session, optionally set the SPF you are wearing, and start. The timer shows elapsed time, accumulated dose in SED, progress towards your threshold and an estimate of the time remaining.
- Log sunscreen. On the UV tab, record that you applied sunscreen, its SPF and whether you are dry, sweating or in water. The card counts down to the next reapplication (2 hours, 80 minutes or 40 minutes).
- Stop and note your skin. Stop the timer when you go inside. The session is saved to Records, and you can say how your skin looked; that answer slightly adjusts future suggested times.
Features
- Current UV index and hourly forecast for today and tomorrow, with the fetch time always shown
- Browser location or a place searched by name
- Sun timer computed from its start time, so reloads and background tabs do not lose time
- UV dose in SED and progress towards a skin-type threshold, with sunscreen SPF taken into account
- Sunscreen reapply countdown for normal, sweating and in-water conditions
- In-page alerts when you reach the suggested time or sunscreen is due, while the page is open
- Session records for the last 7 days and an explanation of how the numbers are calculated
- Export and import of your records as a JSON file
Understanding the UV index and your sun dose
What the UV index measures
The UV index is an international scale for the strength of sunburn-causing ultraviolet radiation at ground level. Each step of 1 corresponds to 25 milliwatts per square metre of erythemally weighted UV. The World Health Organization groups it into bands: 0-2 low, 3-5 moderate, 6-7 high, 8-10 very high and 11 or more extreme. As a general rule, sun protection is recommended from a UV index of 3 upwards.
The index depends mostly on the height of the sun, so it usually peaks around solar noon and is higher in summer and nearer the equator. Altitude raises it, and snow, sand and water reflect UV back at you. Thin cloud reduces it less than people expect, which is why burns on overcast days are common.
From index to dose
What matters for your skin is the total amount received, not the reading at one instant. Dose is often expressed in standard erythema doses (SED), where 1 SED is 100 joules per square metre. One hour in direct sun at UV index 1 gives about 0.9 SED, so an hour at UV index 8 gives about 7 SED. Solvora adds this up minute by minute from the hourly forecast while your timer runs.
The dose that causes visible reddening, the minimal erythema dose, varies widely between people. Very fair skin that always burns may redden after roughly 2 SED, while darker skin tolerates several times more. Skin-type thresholds are averages, which is why the app treats them as a warning point, not a safe limit.
Sunscreen in real life
The SPF on a bottle is measured with a thick layer of 2 mg per square centimetre. Most people apply far less, so real protection is lower than the label. Solvora therefore uses the square root of the SPF when it reduces your dose, treating SPF 30 as roughly 5.5 times protection. Sunscreen also rubs off and washes away: reapply about every two hours, and sooner after sweating, swimming or towelling.
Shade, clothing, a wide-brimmed hat and sunglasses are the first line of protection; sunscreen is for the skin they leave uncovered. If your skin feels hot or looks red, get out of the sun whatever any number says.
Frequently asked questions
Where does the UV data come from?
The web version loads the current UV index and hourly forecast from Open-Meteo using the coordinates of your location or chosen place. The source and fetch time are shown under the gauge.
Is my location stored?
Your coordinates are sent to the forecast service only to fetch UV values. A place you choose by name is saved in this browser so it is used next time; your browser location is not kept.
Will the timer keep counting if I close the tab?
The timer stores its start time, so when you come back the elapsed time and dose are recalculated correctly. However, alerts appear only while the page is open; nothing is sent when the tab or browser is closed.
Where are my records saved?
Only in this browser on this device, with no account. Clearing your browser data deletes them, so use Export in Settings to keep a JSON copy.
How accurate is the suggested time?
It is a rough estimate. Forecasts can differ from what reaches you, and shade, reflection, clothing and how much sunscreen you use all change the real dose.
How is the web version different from the phone app?
The iPhone and Android app can send reminders as notifications even when it is closed. Its paid upgrade adds unlimited record history, weekly and monthly summaries and extra profiles for family members.
Limitations of the web version
- Alerts for the suggested time and sunscreen reapplication appear only while this page is open; no notifications are sent
- Browser location works only while the page is open; otherwise choose a place by name
- Records older than 7 days, summaries and extra profiles are available in the phone app
- UV data comes from Open-Meteo on the web, so values may differ slightly from the phone app
- Forecast hours are shown in your device's time zone, even when you pick a place in another time zone
Disclaimer
UV dose and suggested times in Solvora are rough estimates from forecast data and the skin type you choose. They are not medical advice and do not mean that sun exposure is safe. Protect your skin with shade, clothing and sunscreen, and consult a doctor or dermatologist about any skin concerns.
Phone app
Solvora is also available as an app for phones and tablets: