UV Index Screensaver
The UV Index screensaver is a live world map of the ultraviolet index, glowing from calm green to extreme violet over major cities by how strong the Sun's UV is right now, from the key-less Open-Meteo API. It's free, runs in your browser, and ESC exits.
How the UV Index screensaver works
The saver fetches the current UV index for a built-in list of major world cities (including Toronto, Vancouver, Montréal and Calgary) from the free Open-Meteo API.
Each city is drawn on a world map colored along the WHO UV scale — green is low, yellow and orange moderate to high, red very high, violet extreme.
The extreme spots pulse and are labelled, while cities in night read near zero.
It refreshes every few minutes as the Sun climbs and sinks around the world.
A worked example
At midday the tropics blaze violet at a UV of 12+ while the night side sits at a calm green 0 — a clean picture of where the Sun is fiercest right now, with the highest cities called out.
Settings & tips
- Refresh sets how often the readings update.
- Background sets the map backdrop.
- The legend maps each color to a WHO UV band.
Frequently asked questions
- Is the UV data live?
- Yes. Every city's UV index comes live from Open-Meteo and refreshes every few minutes as the Sun moves.
- What do the colors mean?
- They follow the WHO scale — green low, yellow/orange moderate to high, red very high, violet extreme — the same bands used in sun-safety advice.
- Why are some cities at zero?
- Cities in darkness get no sunlight, so their UV index reads about zero until the Sun rises.
- Does it need a key?
- No. Open-Meteo is free and key-less; the saver only needs an internet connection.
- Is it free?
- Yes — free, no download, in your browser.