Weather: Helsinki — September

September is typically excellent for visiting Helsinki, with average highs of 16°C and around 10 rainy days. Plan your activities accordingly—outdoor sightseeing is best on dry days, while rainy days are perfect for museums and indoor attractions.

Nights in Helsinki during September are cool at around 10°C. Bring a jacket or sweater for evenings, especially if you plan to dine outdoors or take evening walks. The temperature drop from day to night can be noticeable.

With highs of 16°C and lows of 10°C in September, we recommend: Layerable clothing, Light jacket, Compact umbrella, Waterproof jacket/shell. Layering is key as temperatures can vary between air-conditioned interiors and outdoors. Comfortable walking shoes are essential for cobblestone streets.

Helsinki typically sees around 10 rainy days in September. Rain is usually in the form of brief showers rather than all-day downpours, so a compact umbrella is sufficient. Mornings tend to be drier, making them ideal for outdoor sightseeing.

Swimming in Helsinki during September is possible but quite cold, with air temperatures around 16°C. Only brave swimmers venture in without a wetsuit. Consider indoor pools or thermal baths as an alternative if your hotel offers them.

In September, Helsinki gets approximately 13 hours of daylight per day. This affects how much sightseeing you can fit in—longer days mean more time for outdoor activities, while shorter days are perfect for cozy museum visits and early dinners.

Yes, September is peak season in Helsinki. Expect higher prices for accommodation and more crowds at popular attractions, but also the best weather conditions. Book hotels and major attractions in advance to secure availability and better rates.