Free weather calculators — 17+ tools

Weather calculators turn a raw reading off a thermometer or forecast into the number that actually matters: how the air feels on your skin, and when it crosses into dangerous territory. A 35 °C afternoon at 20% humidity and the same temperature at 80% humidity are not the same day — one is hot, the other can be life-threatening. These tools do that translation for you.

The set covers the readings people check most. Wind chill and apparent temperature tell you the “feels-like” figure in cold and mixed conditions; heat index and wet-bulb temperature do it for heat and humidity, with wet-bulb being the one meteorologists watch for true heat danger. Dew point and humidity explain why the air feels muggy or dry, UV index tells you how fast you’ll burn, and density altitude matters to pilots. Practical ones round it out — snow load on a roof and rainfall to gallons for collection.

Every formula here comes from a published meteorological standard — the US National Weather Service heat-index and wind-chill models (Steadman/Rothfusz and JAG/TI) among them — and each calculator page shows its source and a worked example. The math is exact for the inputs you give; real outdoor conditions vary by wind exposure, sun, and your own body, so treat the result as a reliable guide, not a promise.