Helsinki Weather in September
In September, Helsinki averages a high of 15°C (59°F) and a low of 9°C (48°F), from 55 years of daily records (1971–2026).
15°C
Average high
59°F
9°C
Average low
48°F
25°C
Record high
78°F · September 5, 2024
-5°C
Record low
24°F · September 28, 1986
What September Is Like in Helsinki
- Helsinki's hottest September day on record is a recent one: 25°C (78°F) on September 5, 2024.
- September in Helsinki has become 2.6°C (4.7°F) warmer on average: the 2011–2025 average against 1970–1989.
- 8 of the 10 warmest Septembers on record in Helsinki have come since 2011.
- September 2025 was the 3rd warmest September in 55 years of records, 2.7°C (4.9°F) above the long-run average.
At least 1 mm of rain falls on 32% of September days, and the month averages 64 mm in total.
Warmest: 2024 (19.1°C)Latest: 2025 (17.4°C)10-year averageLong-run average (14.9°C)
Look Up a Day in September
See the weather in Helsinki on any September date, year by year.
Source: NOAA GHCN-Daily, Helsinki Kaisaniemi Aws (1971–2026); Helsinki Rautatientori (2009–2015). Averages cover 1971–2026. How we compute this