Helsinki weather in September
September in Helsinki: cool, a little rain, with clean air — a great time to visit.
#5 of 12 months in Helsinki · #356 of 604 destinations to visit in September · comfort 77/100 (tier B)
Updated June 2026 · climate normals from ERA5 reanalysis
Helsinki climate normals — September
| Daytime high | 15°C / 58°F | 🙂 cool |
|---|---|---|
| Nighttime low | 10°C / 50°F | |
| Feels like (high) | 12°C / 54°F | |
| Rainfall | 59 mm / 2.3 in | 🌦 some rain |
| Rainy days | 11 days | |
| Humidity | 81% | 💦 very humid |
| Dew point | 10°C / 49°F | |
| Sunshine | 7.8 h/day | |
| Daylight | 12.9 h | |
| Wind | 19 km/h / 12 mph | |
| Air quality (US AQI) | 37 | 🍃 good |
Monthly averages from ERA5 reanalysis. AQI is the mean US Air Quality Index for the month.
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Helsinki in September — FAQ
- Is September a good time to visit Helsinki?
- September in Helsinki: cool, a little rain, with clean air — a great time to visit. It ranks #5 of 12 months for Helsinki on SeasonMap's comfort score (77/100).
- What is the weather like in Helsinki in September?
- In September, Helsinki averages a daily high of 14.7°C and a low of 10.1°C, with about 59 mm of rain over roughly 11 rainy days.
- What is the air quality in Helsinki in September?
- Helsinki has a mean US Air Quality Index of about 37 in September.