Climate averages 1991–2020
Helsinki weather
in September.
A cool, moderately wet month: the 4th warmest and the 7th driest of the year.
Long-term climate patterns, not a forecast for a particular trip.
September is a cool month in Helsinki: daytime highs average 14.6°C and nights cool to about 9.8°C. By daytime temperature it is the 4th warmest of the 12 months.
Expect about 57 mm of rain on roughly 10 days, which makes September a moderately wet month (the 7th driest of the 12 months). Daylight, from sunrise to sunset, lasts about 12 h 58 min on an average September day.
The nearest other city in this atlas is Vantaa (15 km away). In September its highs average 14.9°C, about as warm as Helsinki, with 57 mm of rain.
Among the 13 cities listed in Finland, Helsinki ranks 3rd of 13 for the warmest September highs and joint 8th of 13 for the driest September (rainfall, lowest first). The mean September high of those 13 cities is 13.8°C; Helsinki is 0.8°C warmer than that mean.
From September to October, average highs fall by 6.5°C to 8.1°C, and monthly rainfall rises from 57 mm to 59 mm.
The annual picture
September in context
Monthly precipitation
Average total · mmAverages from hourly ERA5 reanalysis data. Actual weather varies from year to year. How these numbers are calculated
Every month, side by side
Helsinki climate table
| Month | Average highHigh / low | Average low | Precipitation mm/month | Wet days ≥1 mm/day | Daylight hours/dayDaylight h/day |
|---|---|---|---|---|---|
| January | -2.1°C-6.0°C | -6.0°C | 48 | 10.9 | 6.87 h |
| February | -2.9°C-7.1°C | -7.1°C | 41 | 9.3 | 9.19 h |
| March | 0.7°C-4.6°C | -4.6°C | 37 | 8.5 | 11.712 h |
| April | 6.9°C0.3°C | 0.3°C | 37 | 8.7 | 14.515 h |
| May | 13.1°C6.0°C | 6.0°C | 44 | 8.9 | 17.217 h |
| June | 17.3°C10.8°C | 10.8°C | 72 | 11.7 | 18.819 h |
| July | 20.8°C14.6°C | 14.6°C | 76 | 11.9 | 18.118 h |
| August | 19.6°C13.9°C | 13.9°C | 76 | 12.3 | 15.716 h |
| September, selected | 14.6°C9.8°C | 9.8°C | 57 | 10.4 | 13.013 h |
| October | 8.1°C4.4°C | 4.4°C | 59 | 11.1 | 10.210 h |
| November | 3.3°C0.3°C | 0.3°C | 59 | 11.5 | 7.68 h |
| December | 0.1°C-3.2°C | -3.2°C | 55 | 12.2 | 6.06 h |
Precipitation (rain or snow, as water) is the average of the 30 separate monthly totals. A wet day is a local calendar day with at least 1 mm of precipitation. Daylight is the calculated sunrise-to-sunset length, not measured sunshine.
Compare places
September in nearby cities
- Vantaa in SeptemberFinland · 15 kmHigh 14.9°C · Low 9.0°C · 57 mm rain
- Espoo in SeptemberFinland · 16 kmHigh 14.5°C · Low 10.0°C · 55 mm rain
- Tallinn in SeptemberEstonia · 82 kmHigh 15.3°C · Low 9.9°C · 60 mm rain
- Lahti in SeptemberFinland · 99 kmHigh 14.1°C · Low 8.5°C · 51 mm rain
- Kouvola in SeptemberFinland · 124 kmHigh 14.2°C · Low 8.4°C · 53 mm rain
- Turku in SeptemberFinland · 150 kmHigh 15.0°C · Low 8.8°C · 58 mm rain
- Tampere in SeptemberFinland · 160 kmHigh 13.5°C · Low 8.8°C · 53 mm rain
- Lappeenranta in SeptemberFinland · 203 kmHigh 13.9°C · Low 8.6°C · 56 mm rain
Read the numbers correctly
Climate, not a promise.
These patterns help compare months. They cannot tell you the weather on a specific day of your trip.
Sources, method and limitsHow these numbers are made (what the highs, lows and rain days mean, the sources and the model cell used for Helsinki) is explained once on the Helsinki year overview and on the Sources, method and limits page.
Vantaa lies in the same rainfall cell, so its rainfall figures are identical to these; temperatures differ because they come from smaller 0.1° cells.