Weather in Helsinki in September 2025
Average weather
Average temperature in Helsinki in September
The temperature in September is +18°C on average, with a range between a maximum of +21°C during the day and a minimum of +6°C at night.
The average maximum temperature goes down 20% by the end of the month, compared with the beginning of the month, from +19°C to +16°C.
Is Helsinki warm or cold in September?
Helsinki is typically mild in September.
Maximum temperatures go down compared to the previous month from +19°C to +14°C. The minimum temperature also goes down from +13°C to +9°C.
Pack a light jacket as it will be warm in the day and cool in the evenings.
Take a look at how September is compared to other months in Helsinki:
Water temperature in Helsinki in September
Water in Helsinki in September is Cold. It varies from +1°C to +20°C, with an average of +10°C. This is almost similar to the air temperature, which averages +14°C.
The water temperature in September is one of the warmest of the entire year:
Can you swim in Helsinki in September?
Climate in Helsinki in September
| August | September | October | ||||
|---|---|---|---|---|---|---|
| Avg. temperature | ||||||
| +19°C | +14°C | +9°C | ||||
| Min. temperature | ||||||
| +3°C | 0°C | -8°C | ||||
| Max. temperature | ||||||
| +29°C | +22°C | +18°C | ||||
| Rainfall | ||||||
| 83 mm | 78 mm | 83 mm | ||||
| Wind | ||||||
| 3 m/s | 4 m/s | 4 m/s | ||||
| Avg. water temperature | ||||||
| +13°C | +10°C | +7°C | ||||
| Humidity | ||||||
| 76% | 81% | 84% | ||||
| Air pressure | ||||||
| 1011 HPa | 1011 HPa | 1011 HPa | ||||
| Sunny days | ||||||
| 8 | 5 | 4 | ||||
| Cloudy days | ||||||
| 5 | 8 | 8 | ||||
| Rainy days | ||||||
| 15 | 16 | 17 | ||||
| Snowy days | ||||||
| 0 | 0 | 2 | ||||
September weather is still as ok as in August. It’s getting colder in September. From +19°C in the day, the average maximum temperature lowers to +14°C. As September arrives, the amount of rainfall goes down. On average, the rainfall volume decreases from 83 mm to 78 mm. Humidity rises from 76% to 81%. Winds are stronger in comparison to August, going up from 3 m/s to 4 m/s on average. The days becoming less sunny, going from 8 sunny days in August to 5 in September.
October brings much the same weather, it remains ok.
Wind
The average wind speed is 6 m/s getting up to 11 m/s which is a medium breeze. You can feel it, especially getting out of the water.
The average wind speed in Helsinki is gradually increasing during September, going from 5 m/s to 9 m/s over the course of the month.
Rain
How was the weather last September in Helsinki?
Climate Change over Years
The climate in Helsinki in September has not changed much over the last 43 years.
The average temperature was the lowest in 1987 (+5°C) and the highest in 2020 (+11°C). The driest year was 2002 with only 248 mm of rainfall, and the wettest year was 2020 with 1153 mm.
FAQ
Is September a good time to visit Helsinki?
Can you sunbathe in Helsinki in September?
Can you swim in Helsinki in September?
Is Helsinki rainy in September?
Is it sunny in Helsinki in September?
Other cities in Finland
Monthly weather in Helsinki
Source of the data
For this page, we’ve looked at the typical weather in Helsinki, based on historical hourly weather data from January 1, 1979, to December 31, 2023.
For past dates, we show actual recorded data at the location at that time. Forecasts are based on recorded weather during that day of the year, averaged over the total years for which we have records (unless stated otherwise). The daily temperature is the highest recorded temperature in the shadow during that day.