isithot.today

How it works

isithot.today answers one question: will today feel hot where you are? Here is how we get from a pile of forecasts to a single Yes, Almost or No.

isithot.today, isitwet.today and willitsnow.today are one service with three questions: will today feel hot, will it rain, and will it snow? Each site opens on its own question, and the Hot, Wet and Snow switch at the top of the page swaps between them.

Several forecasts, one answer

Weather services run their own computer models, and they rarely agree to the degree. We ask 8 of them for today's high: ECMWF, GFS, ICON, UKMO, Météo-France, MET Norway, GEM and JMA. Some models do not cover every place, so we use whichever ones answer.

With five or more forecasts we drop the single highest and lowest, then average the rest. That keeps one wild forecast from dragging the answer around. We do the same for the "feels like" temperature, which accounts for humidity and wind.

How much the forecasts agree

Under the answer you will see something like "5 of 6 forecasts agree within 2°". Each dot on the strip is one forecast; the shaded band covers 2° either side of the blended high. When most dots sit inside the band, you can trust the answer. When they are scattered, the weather is genuinely uncertain, and it is worth checking a detailed forecast.

Hot for where you are

24°C feels hot in Newcastle and mild in Seville. So we compare today's feels-like high with the long-term climate where you are: how warm your coldest and warmest months normally get. Half of the verdict comes from that local comparison and half from the temperature itself, because people feel both. A few common-sense limits apply: below 18°C it is never "hot", and above 25°C it is never "cold".

The "warmer than usual" line compares today's high with the normal high for this date. Normals come from NASA's long-term records on a grid about 50 km across, so they describe the regional average; coasts, hills and city centres can run a degree or two either side.

Is it wet?

For rain, we ask 8 forecast models how much they expect, hour by hour. A model "expects rain" when it forecasts at least 1 mm for the day. For a shorter stretch, like the rest of an evening, less is enough: 0.2 mm for each hour that is left. The share of models expecting rain is the chance. When 60% or more of them do, the answer is Yes; from 25% it is Maybe. How much rain comes from the middle forecast (the median), so one model's downpour cannot make the day wet on its own.

Today means the rest of today, from now until midnight. Rain that has already fallen no longer counts, so the answer can change through the day. When most of it is forecast to fall as snow, judged by the same rule as "Will it snow?", the answer says so.

This week adds up each model's rain for the rest of today and the next six days, and compares the total with the rainfall that is normal there at this time of year, from NASA POWER's long-term records.

Will it snow?

For snow, we ask 8 forecast models how much they expect, hour by hour, as a depth of fresh snow: 7 cm for every 10 mm of water, the usual ratio. A model "expects snow" when it forecasts at least 0.5 cm for the day. For a shorter stretch, like the rest of an evening, less is enough: 0.1 cm for each hour that is left. The share of models expecting snow is the chance. When 60% or more of them do, the answer is Yes; from 25% it is Maybe. How much snow comes from the middle forecast (the median).

Rain and snow are told apart by one rule, so Wet and Snow always agree: in an hour warmer than 2.5°C nothing counts as snow, whatever a model says. When the answer is No, it says why: too warm, rain rather than snow, or simply dry, with the lowest temperature expected.

This week is Yes when any day brings snow. Where NASA POWER's long-term records cover it, we also say whether snow is rare or common there at this time of year, and compare the week with normal. Snow depends so much on height that we only do this where the records' 50 km grid cell is within 300 m of the place's height. Amounts are fresh snowfall, not what will be lying on the ground: some of it may melt as it lands.

Your location

We start with an approximate location from your internet connection. If you allow it, your device location is used instead, rounded to about 5 km before it leaves your browser. You can also search for any place. Read more in our privacy notice.

Where the data comes from

Forecasts are estimates. For anything that matters, like heat health or flood warnings, check your national weather service.