The first 3 days are right about 85% of the time, days 7-10 about 60%, and days 11-14 about 45%. Beyond two weeks the atmosphere is chaotic, so no daily forecast is meaningful — that is why days 15-30 on our pages show season-typical values from the 1991-2020 climate record instead of pretending to be precise.
Which days are a real forecast and which are climate averages?
Days 1-14 come live from weather models (UKV, ECMWF, GFS) and update several times a day. Days 15-30 are typical ranges for those dates, built from 30 years of climate data for each town — useful for planning, not an exact prediction.
Can I see if it will rain on a specific date three weeks ahead?
No serious forecast can promise rain or sunshine on one specific day that far out. The 30-day page shows what is typical for those dates; check back once the date is within 14 days for a real model forecast, and within 48 hours for hour-by-hour detail.
How often are the long-range pages updated?
The model part (days 1-14) refreshes several times a day for every town listed here. The climate part is recalculated from the 1991-2020 normals and stays stable within the month.
About synthesised forecasts
Climate averages 1991-2020 (ERA5)
Real weather forecasts have a horizon of ~14 days — beyond that the uncertainty becomes larger than the variation. For days 15-30 we show season-typical values: the month’s average maximum and minimum from the 1991-2020 climate record, adjusted for the location and with a mild weekly variation. Good for planning ("roughly how warm does it get in London in the third week of July") — NOT an exact forecast for a specific day.
Choose a city for a 30-day outlook. Days 1-14 come from weather models; days 15-30 are synthesised from 1991-2020 climate averages — season-typical values with weekly variation, NOT an exact forecast that far ahead.
DATA
Forecasts from the UK Met Office UKV model, global weather models and official UK environmental data · Met Office UKV model · Environment Agency · Copernicus CAMS · NOAA