Helsinki weather in September
Temperature, sea and sunshine in September: long-term averages from 30 years of weather data, not a forecast.
Holiday weather in September
Good
Best time to visit: June – August
What is the weather like in Helsinki in September?
In September, Helsinki is cool: daytime highs average 15 °C, and nights cool down to about 10 °C. The sea averages 14.8 °C – swimming is only for the hardy. Expect around 6 hours of sunshine a day. Rain is frequent, with about 10 rainy days and 58 mm in total. All in all, September is a good month for a holiday in Helsinki.
September compared
How the weather changes from August to October. Tap a month to open it.
| AugustAug | SeptemberSep | OctoberOct | |
|---|---|---|---|
| Score | 77 | 60 | 17 |
| Day | 20° | 15° | 9° |
| Night | 14° | 10° | 5° |
| Sea | 17° | 15° | 11° |
| Sun | 8 h | 6 h | 3 h |
| Rain days | 13 | 10 | 12 |
More details for September
- Daylight
- 13 h 0 min06:45 – 19:46
- UV index
- 2 · lowclear sky, noon (estimate)
- Muggy days
- 0 daysdew point 18 °C or more
- Wind
- 19 km/haverage daily peak
- Cloud cover
- 67 %on average
- Hot days
- 0 days30 °C or more
- Snow days
- 0 days1 cm or more of fresh snow
- Time zone
- UTC+3Europe/Helsinki
How the score comes together
- Temperatureweight 50 %69 %
- Sunshineweight 20 %42 %
- Few rainy daysweight 30 %56 %
Each factor is rated from 0 to 100 % and weighted for the travel style “City break”.
What to pack in September
- A jumper for the evenings
- Rain jacket or umbrella
Helsinki in September: quick answers
Is Helsinki hot in September?
No. In September, Helsinki is cool: daytime highs average 15 °C and nights drop to about 10 °C.
Can you swim in Helsinki in September?
Only if you don't mind cold water: in September the sea averages just 14.8 °C. Comfortable swimming temperatures are not reached at any time of year.
Does it rain much in Helsinki in September?
Rain is frequent, with about 10 rainy days and 58 mm in total.
Helsinki month by month
The whole year in HelsinkiAll destinations: Finland
Climate averages 1996–2025, not a forecast. Data: Copernicus ERA5 / ERA5-Land via Open-Meteo.com (CC BY 4.0), NOAA OISST, GeoNames (CC BY 4.0)