Heat Index Screensaver
The Heat Index screensaver is a live world map of the apparent temperature — how hot or cold it actually feels with humidity and wind — glowing blue to red across major cities, from the key-less Open-Meteo API. It's free, runs in your browser, and ESC exits.
How the Heat Index screensaver works
The saver asks Open-Meteo for the apparent (feels-like) temperature at a built-in list of major world cities, including Toronto, Vancouver, Montréal and Calgary.
Each city is plotted on a world map as a glowing dot colored from deep blue when it feels frigid to red when it feels dangerously hot.
Dots grow at the extremes — both blistering heat and biting cold — so the day's hot and cold spots stand out.
It refreshes every few minutes so the map tracks the warming and cooling through the day.
A worked example
In a summer heatwave you'll see Phoenix glaring red at a feels-like 46° while a Canadian winter night turns Calgary deep blue — the labelled hottest and coldest cities calling out the extremes.
Settings & tips
- Units switches between Celsius and Fahrenheit.
- Refresh sets how often the readings update.
- Background sets the map backdrop.
Frequently asked questions
- Is the data live?
- Yes. The feels-like temperature for every city comes live from Open-Meteo and refreshes every few minutes.
- What is apparent temperature?
- It's how hot or cold it actually feels once humidity, wind and sun are factored in — often quite different from the raw thermometer reading.
- Does it need a key?
- No. Open-Meteo is free and key-less; the saver only needs an internet connection.
- Which cities are shown?
- A built-in spread of major world cities across every continent, including several Canadian cities.
- Is it free?
- Yes — free, no download, in your browser.