September in Helsinki marks the transition from summer to autumn. Expect average high temperatures around 14C (57F) and lows around 7C (45F). Rainfall becomes more frequent than in the summer months, with an average of around 60mm spread across the month. Daylight hours decrease noticeably, offering around 13 hours of daylight at the beginning of the month and closer to 10 by the end. This period experiences a shift in prevailing wind directions, often coming from the west or southwest.
Understanding the climatic conditions of this period is valuable for various reasons. For travelers, it informs packing choices, suggesting layers to accommodate fluctuating temperatures and potential rain. For residents, it signals the approach of winter, prompting preparations for colder weather and shorter days. Historically, September has been a significant month for Helsinki, marking the end of the harvest season and the beginning of preparations for the long winter ahead. This seasonal shift is deeply ingrained in the city’s cultural heritage and continues to influence local activities and traditions.