Helsinki Weather in September
Finland · Subarctic climate · Data averaged from 2020-01-01 to 2024-12-31 (5 years)
September in Helsinki sees average temperatures ranging from a low of 10.2°C (50.4°F) to a high of 15.5°C (59.9°F), with a mean of 12.9°C (55.2°F). Compared to the annual average of 6.8°C (44.2°F), this month is 6.1°C warmer than the yearly norm. Precipitation averages 69.6mm, making it approximately 1.0mm wetter than the monthly average of 69.0mm. The city receives an average of 8.6 hours of sunshine per day during September, with relative humidity averaging 80.3%. Wind speeds reach an average maximum of 21.9 km/h. For travelers, this month offers a temperature experience in Helsinki, with wetter-than-average conditions compared to the rest of the year.
If you're planning outdoor activities in Helsinki, daylight is the variable that matters most. I did a sea kayak tour in June at 10pm — full sun, 18°C, surreal. December gives you 6 hours of gray light, which limits everything. The Nordic summer (June-August) is the outdoor window: 18-22°C, 19 hours of daylight, perfect for island-hopping by ferry. Winter is its own adventure: -5°C, snow cover from January-March, and the sauna-ice-swim cycle is a Helsinki essential. Pack windproof layers year-round — the Baltic breeze cuts hard. September brings fall colors and fewer tourists; my favorite hiking month.
September vs Adjacent Months
| Metric | August | September | October |
|---|---|---|---|
| Mean Temp | 17.2°C (63.0°F) | 12.9°C (55.2°F) | 8.0°C (46.4°F) |
| Rainfall | 97.1mm | 69.6mm | 86.2mm |
| Sunshine | 11.1 hrs | 8.6 hrs | 5.1 hrs |
| Humidity | 79.5% | 80.3% | 83.8% |
| Wind | 21.3 km/h | 21.9 km/h | 25.8 km/h |
| Rainy Days | 19.6 | 15.6 | 20.0 |
| Snowfall | 0.0 cm | 0.0 cm | 0.5 cm |
Seasonal Context
September falls in Autumn in the Northern Hemisphere. Autumn sees temperatures gradually cooling from summer highs. For travelers visiting Helsinki in September, the data indicates mixed conditions based on the combination of temperature, precipitation, and daylight hours.
Frequently Asked Questions
What is the average temperature in Helsinki in September?
The average temperature in Helsinki during September ranges from 10.2°C (50.4°F) to 15.5°C (59.9°F), with a mean of 12.9°C (55.2°F).
How much does it rain in Helsinki in September?
Helsinki receives an average of 69.6mm of precipitation in September, spread across approximately 15.6 rainy days.
What should I pack for Helsinki in September?
Based on September weather data, pack warm layers, a medium jacket, and waterproof outerwear.
Is September a good time to visit Helsinki?
September is a cooler month, suitable for travelers who prefer mild weather and fewer crowds. Pack warm layers and enjoy indoor attractions.
Other Months for Helsinki
Cities with Similar September Climate (Subarctic)
Data Source: Open-Meteo historical archive (2020-01-01 to 2024-12-31). Daily measurements aggregated into monthly climate normals. Coordinates: 60.17°, 24.94°. Timezone: Europe/Helsinki. Last updated: 2026-07-30.