WEATHER · CLIMATE NORMALS · 1991–2020
Helsinki Climate — Averages by Month
What the weather in Helsinki, FIaverages across a standard 30-year period. Each month's figure is the 1991–2020 mean temperature and total rainfall from the ERA5 reanalysis — the long-run normal a place settles around, not a forecast for any particular day.
Month-by-month normals
| Month | Avg temperature | Avg rainfall |
|---|---|---|
| January | -4.1 °C | 57.1 mm |
| February | -4.9 °C · coldest | 47.7 mm |
| March | -1.6 °C | 42.0 mm |
| April | 4.1 °C | 41.2 mm |
| May | 10.2 °C | 47.8 mm |
| June | 14.7 °C | 76.4 mm |
| July | 17.9 °C · warmest | 81.5 mm |
| August | 16.4 °C | 81.9 mm · wettest |
| September | 11.6 °C | 63.5 mm |
| October | 6.0 °C | 66.5 mm |
| November | 1.6 °C | 66.6 mm |
| December | -1.6 °C | 64.5 mm |
How to read these numbers
These are reanalysis normals, not readings from a single weather station. They come from the ERA5 0.25° (~25 km) global reanalysis grid, sampled at the grid cell nearest Helsinki — centred at 60.25°N, 25.00°E. A reanalysis blends observations with a physics model onto an even grid, so a coastal or mountain city's cell can read a little cooler, warmer, wetter or drier than the city centre itself. The month-to-month shape — when it's hot, when it rains — is what these normals capture best.
“Normal” means the 1991–2020 average, the current World Meteorological Organization standard period. A normal is what a place tends toward over decades — any single day, month or year can and will depart from it.