Light rain from around 22:30.
drizzlelightdry
Weather radars around the UK send out radio waves and pick up the echo from raindrops in the air. The heavier the rain, the stronger the echo. The Met Office combines up to 16 radars into one map of the UK, made of 1 km squares, and publishes a new one every 15 minutes.
Each picture shows where it was raining when it was taken. The colour shows how heavy the rain was, from blue for drizzle through green, yellow, orange and red to purple for a downpour.
In the chart, the dark line is the rain measured at your location, up to the newest picture. On the map and in the chart, everything after that picture is forecast, even ‘now’, because the newest picture is already 5 to 20 minutes old. Slide along the chart to see the map at that time.
Areas of rain are carried along by the wind high above the ground, which can blow in a different direction from the wind you feel. They often keep a similar shape for an hour or more. Comparing the last three radar pictures, taken over half an hour, shows which way the rain is moving and how fast.
The forecast moves the rain on in the same direction and at the same speed. A shower 10 km west of you, moving east at 30 km/h, reaches you in about 20 minutes. This works best for large areas of rain. Showers can change within half an hour.
Rain doesn’t only move. Showers grow and weaken, and new ones form where there was no rain before. This can’t be predicted exactly, so the forecast is made 20 times, each with a slightly different speed, direction and strength of the rain.
Each blue line in the chart is one of these forecasts. The higher the line, the heavier the rain. The more lines show rain at a time, the more likely rain is then.
Where the lines stay close together, the forecast is fairly certain. Further ahead, they spread apart. None of them can show a shower before it forms, even when they agree.
The sentence at the top says what the lines agree on. If it doesn’t say ‘likely’, ‘should’, ‘may’ or ‘possible’, nearly all the lines agree. ‘Likely’ and ‘should’ mean most do; ‘may’ and ‘possible’ mean only some do.
After about two hours, a traditional weather forecast is more useful.
It is most reliable for the next half hour, and for longer when a large area of rain is moving steadily. Showers and thunderstorms are harder: they can form or die out within half an hour, and new ones are only forecast once the radar sees them.
Every 15 minutes a new radar picture shows where the rain actually went, and the forecast is updated from it. Changes of a few minutes are normal. If the end time keeps moving later, the rain is moving more slowly than expected or more rain is forming behind it.
Most weather apps show a forecast from a computer model, given hour by hour. It can say that showers are likely in the afternoon, but not exactly when one reaches you. This page starts from where the rain is now, so for the next two hours it is usually more precise. For later in the day, use the weather app.
It is not a Met Office forecast. It uses their radar pictures, but the forecast is calculated by this site, with a method called STEPS. The Met Office and the Australian Bureau of Meteorology developed it; this site uses the open-source version in pysteps.
The last three radar pictures show which way the rain is moving and how fast. The newest picture is moved on along that motion, 15 minutes at a time, and the minutes in between are filled in.
Small patches of rain change faster than large areas, so they fade out of the forecast sooner. Each of the 20 forecasts adds slightly different random changes to the rain and its motion. The forecast on the map leaves out the random changes, which is why it looks smoother further ahead.
Bowler, Pierce and Seed (2006), STEPS, Quarterly Journal of the Royal Meteorological Society. Pulkkinen et al. (2019), pysteps, Geoscientific Model Development.
The radar measures rain in the air, not on the ground. If the air below is dry, light rain can evaporate before it lands. This happens most often at the edges of rain areas and when rain is just starting.
Radar often misses drizzle. The drops are tiny and reflect little, and drizzle often falls from cloud so low that the radar beam passes over it, especially far from the nearest radar or behind hills.
Yes, but as rain. The radar can’t tell snow, sleet or hail from rain, and their strength can be wrong. Melting snow often looks heavier than it is.
Rain is measured in millimetres per hour: how deep the water would be on flat ground after an hour of rain at that strength. The names below are this site’s own; other services draw the lines differently.
| Drizzle | 0.1–0.5 mm/h | tiny drops; you get damp slowly |
|---|---|---|
| Light rain | 0.5–2 mm/h | a hood or umbrella is enough |
| Moderate rain | 2–8 mm/h | you get wet quickly without a coat |
| Heavy rain | 8–25 mm/h | loud on roofs; puddles form quickly |
| Downpour | over 25 mm/h | water runs along the street; rarely lasts long |
Your browser only shares your location if you allow it. It is used to look up the forecast for your 1 km square and is not stored on the server. This browser remembers the last place you chose, so the forecast is there straight away next time. You can also type in a town or postcode.