London weather by month
London runs from about 5°C in January to 19°C in August, with September the wettest month at 169 mm.
warmest month
August
19°C
coolest month
January
5°C
wettest month
September
169 mm
worst air month
March
13 µg/m³
The whole year, month by month.
| Month | Avg temp | Rain | Sun | PM2.5 |
|---|---|---|---|---|
| January | 5°C | 67 mm | 148 h | 8 |
| February | 9°C | 110 mm | 101 h | 8 |
| March | 8°C | 81 mm | 184 h | 13 |
| April | 10°C | 65 mm | 246 h | 9 |
| May | 14°C | 75 mm | 301 h | 9 |
| June | 16°C | 25 mm | 383 h | 7 |
| July | 18°C | 85 mm | 324 h | 6 |
| August | 19°C | 29 mm | 310 h | 7 |
| September | 15°C | 169 mm | 230 h | 6 |
| October | 12°C | 83 mm | 186 h | 8 |
| November | 8°C | 63 mm | 116 h | 7 |
| December | 8°C | 41 mm | 76 h | 8 |
About 2,605 hours of sun a year. Roughly 91 rainy days a year.
These are long-run climate normals, not a forecast. A given year can sit well outside them. PM2.5 is a global model: near the coast it counts sea salt as fine particulate and reads high against ground stations, sometimes by a factor of two. Use the shape of the year, not the absolute number.
where these numbers come from
- · Temperature, rainfall and sunshine: ECMWF ERA5 reanalysis climate normals via Open-Meteo (CC BY 4.0), fetched once and stored.
- · PM2.5: Copernicus CAMS reanalysis, monthly means. Modelled, not station readings; near coasts CAMS counts sea salt as PM2.5 and reads high.
Last reviewed 2026-05-22. Full method, licences and the list of sources we rejected are on the methodology page.