The calculators on this page turn raw weather numbers into something useful. A thermometer reading on its own does not say how cold it will actually feel in the wind, whether a humid afternoon counts as dangerous heat, or what temperature a fog is likely to form at — each of those needs a different, well-established formula applied to the same handful of inputs: air temperature, humidity and wind speed. That is what this section collects: temperature conversion between Celsius, Fahrenheit and Kelvin, and five further calculators — feels-like temperature, wind chill, heat index, dew point and relative humidity — each built on the formula meteorologists themselves use, not a simplified approximation invented for this page.
The temperature strip near the top of every page in this section shows today's mean temperature for ten countries, pulled daily from Meteostat's public station data — a live reference point to check a converted or calculated figure against, not a forecast.
Why the thermometer alone is not the full picture
Air temperature is the easiest weather quantity to measure and the least complete on its own. The same 10 °C reading feels mild on a calm, dry day and bitter on a windy, damp one; the same 32 °C reading is comfortable at low humidity and dangerous at high humidity. Meteorological agencies developed wind chill and heat index specifically to close that gap — both take the measured air temperature and adjust it into a single number that tracks what the body actually experiences, using formulas built from physiological research rather than guesswork. Wind chill applies at the cold end, heat index at the hot end, and the general-purpose feels-like calculator blends temperature, humidity and wind into one figure that spans both.
Temperature, dew point and humidity are three views of the same air
Air temperature, dew point and relative humidity describe the same parcel of air from three different angles, and any two of them determine the third. Dew point is the most direct measure of how much moisture the air actually holds — it is the temperature the air would need to cool to before that moisture condenses into dew, fog or mist. Relative humidity, by contrast, is a ratio that changes with temperature even when the moisture content does not, which is why a muggy morning and a muggy afternoon can report very different humidity percentages while the dew point barely moves. Meteorologists generally treat dew point as the more useful figure for judging how the air actually feels, precisely because it does not have that quirk.
Converting between Celsius, Fahrenheit and Kelvin
The temperature converter, the dedicated Celsius to Fahrenheit page and the reference chart all handle the same linear conversion between the three common temperature scales — useful for reading a US weather forecast in Fahrenheit, an oven temperature in a foreign recipe, or a school physics problem that expects Kelvin. The formula never changes; these pages exist as different ways of reaching the same number, whichever direction you are starting from.
Formulas, not rules of thumb
Every calculator in this section uses a formula published by a national meteorological agency — the US National Weather Service for heat index, Environment Canada for wind chill, the Australian Bureau of Meteorology for the general feels-like figure, and the Magnus-Tetens approximation, standard across the field, for dew point and relative humidity. Each one is a statistical or physical model fitted to real conditions, not an invented shortcut, and each comes with its own valid range stated on its own page — wind chill, for instance, is only meaningful in cold, breezy weather, and heat index only in warm, humid weather. Outside those ranges the plain air temperature remains the more honest number, and the pages say so rather than returning a figure that looks precise but is not.
What to wear
The what to wear calculator is the practical endpoint of the rest of this section: instead of a temperature or a percentage, it turns air temperature, wind and rain into a plain-language clothing suggestion — the question most people are actually trying to answer when they check the weather in the first place.