September weather forecastHelsinki, Finland

A scenic reflection in the water of the illuminated city of Helsinki in Finland

September

Weather in September

Entering autumn, September in Helsinki shifts the weather narrative towards a cooler milieu. The city's foliage dons autumn hues matching the moderating temperatures presetting a high of 14.6°C (58.3°F). Despite reduced sunlight and daylight hours shortened to 12.9h, the ambiance stays invigorating. A higher frequency of rainfall can be expected, lending a characteristic moistness to the autumn air. By September, nature enthusiasts would find Helsinki profoundly appealing for its vibrant leafy landscapes.

Temperature

September brings a decrease in the average high-temperature, falling from August's enjoyable 19.8°C (67.6°F) to a moderate 14.6°C (58.3°F). Helsinki experiences an average temperature drop to a frosty 8.7°C (47.7°F) during September nights.

Rainfall

In Helsinki, in September, during 14 rainfall days, 56mm (2.2") of precipitation is typically accumulated. In Helsinki, during the entire year, the rain falls for 182 days and collects up to 655mm (25.79") of precipitation.

Snowfall

April through October are months without snowfall.

Sea temperature

In Helsinki, the average seawater temperature in September is 14°C (57.2°F).
Note: Dipping into 14°C (57.2°F) below 10°C (50°F) is possible with the right protection; absent that, anticipate cold shock and hampered breathing. Swimming momentarily at 13°C (55.4°F) can be jarring.

Daylight

In Helsinki, the average length of the day in September is 12h and 52min.
On the first day of the month, sunrise is at 06:16 and sunset at 20:24. On the last day of September, in Helsinki, sunrise is at 07:24 and sunset at 18:55 EEST.

Sunshine

In September, the average sunshine in Helsinki is 5h.

UV index

The average daily maximum UV index in September is 3. A UV Index reading of 3 to 5 represents a moderate threat to health from exposure to the Sun's UV radiation for average individuals.
Note: The average daily UV index of 3 in September transforms into the following instructions:
Take measures. Individuals with light skin might experience burns in under 30 minutes. When the Sun is at its strongest around midday, find shade and limit exposure. To cut down UV radiation exposure by about half, sport a wide-brim hat.

Updated: Jan 31, 2024
Published by: Weather Atlas | About Us
Data Sources | Weather Forecasting & Climate

Frequently asked questions

The average high-temperature, in September, in Helsinki, is 14.6°C (58.3°F), while the average low-temperature is 8.7°C (47.7°F).

In Helsinki, Finland, in September, it is raining for 14 days, with typically 56mm (2.2") of accumulated precipitation.

In Helsinki, Finland, snow does not fall in April through October.

In September, the average sea temperature in Helsinki is 14°C (57.2°F). Swimming in 14°C (57.2°F) is considered dangerous. Unprotected immersion in temperatures below 10°C (50°F) causes quickly maximum intensity cold shock with hyperventilation.

In September, the average day length is 12h and 52min.

On the first day of September, sunrise is at 06:16 and sunset at 20:24. On the last day of the month, sunrise is at 07:24 and sunset at 18:55 EEST.

In September, the average sunshine duration is 5h.

In Helsinki, Finland, the average daily maximum UV index in September is 3. A UV Index estimate of 3 to 5 represents a medium hazard to health from exposure to Sun's UV rays.

Today

Tomorrow

Long-term

Year J F M A M J J A September O N D

Aug

September

Oct

Average high temperature

19.8°C

14.6°C

9°C

Average low temperature

Average rainfall

Average rainfall days

Average snowfall

0mm

Average sea temperature

Average daylight

Average sunshine

Average UV index

Average temperature in September
Helsinki, Finland

Average high temperature in September: 14.6°C

The warmest month (with the highest average high temperature) is July (21.5°C).
The month with the lowest average high temperature is February (-1.9°C).

Average low temperature in September: 8.7°C

The month with the highest average low temperature is July (14.2°C).
The coldest month (with the lowest average low temperature) is February (-7.4°C).

Average rainfall in September
Helsinki, Finland

Average rainfall in September: 56mm

The wettest month (with the highest rainfall) is August (80mm).
The driest month (with the least rainfall) is April (32mm).

Average rainfall days in September
Helsinki, Finland

Average rainfall days in September: 14 days

The month with the highest number of rainy days is December (20 days).
The months with the least rainy days are April and May (11 days).

Average snowfall in September
Helsinki, Finland

Average snowfall in September: 0mm

The month with the highest snowfall is February (230mm).
The months with the least snowfall are April, May, June, July, August, September and October (0mm).

Average sea temperature in September
Helsinki, Finland

Average sea temperature in September: 14°C

The best month for swimming (with the highest average sea temperature) is August (16°C).
The coldest months (with the lowest average sea temperature) are February and March (1°C).

Average daylight in September /
Average sunshine in September
Helsinki, Finland

Average daylight in September: 12h and 54min

The month with the longest days is June (Average daylight: 18h and 48min).
The month with the shortest days is December (Average daylight: 6h and 0min).

Average sunshine in September: 5h and 0min

The month with the most sunshine is June (Average sunshine: 9h and 54min).
The month with the least sunshine is December (Average sunshine: 0h and 54min).

Average UV index in September
Helsinki, Finland

Average UV index in September: 3

The months with the highest UV index are June and July (UV index 5).
The months with the lowest UV index are January, February, November and December (UV index 0).