Heidelberg weather by month
Heidelberg runs from about 2°C in January to 22°C in August, with May the wettest month at 162 mm.
warmest month
August
22°C
coolest month
January
2°C
wettest month
May
162 mm
worst air month
December
16 µg/m³
The whole year, month by month.
| Month | Avg temp | Rain | Sun | PM2.5 |
|---|---|---|---|---|
| January | 2°C | 82 mm | 125 h | 16 |
| February | 8°C | 109 mm | 134 h | 11 |
| March | 9°C | 76 mm | 222 h | 15 |
| April | 11°C | 106 mm | 263 h | 9 |
| May | 15°C | 162 mm | 284 h | 7 |
| June | 18°C | 100 mm | 343 h | 7 |
| July | 20°C | 101 mm | 370 h | 6 |
| August | 22°C | 69 mm | 356 h | 8 |
| September | 16°C | 121 mm | 240 h | 7 |
| October | 12°C | 121 mm | 181 h | 9 |
| November | 6°C | 80 mm | 122 h | 15 |
| December | 3°C | 45 mm | 87 h | 16 |
About 2,727 hours of sun a year. Roughly 118 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 2026-05-23. Full method, licences and the list of sources we rejected are on the methodology page.