Last updated: August 21, 2025
Experience the charm of Mariehamn, Åland Islands in September, where autumn gently begins to weave its magic. With a maximum temperature reaching 20°C (68°F) and a comfortable average of 14°C (57°F), the climate offers a mild escape. As the days transition, temperatures can dip to a refreshing 8°C (46°F), perfect for cozying up. Expect a moderate precipitation total of 56 mm (2.2 in) over approximately 11 days, creating a lush landscape. The air hangs with a noticeable humidity of 85%, giving the environment a serene and fresh feel, ideal for exploring the beautiful scenery and cultural offerings of this unique island community.
In September, Mariehamn experiences a gentle transition from the warmth of summer to the cooler embrace of autumn. With minimum temperatures hovering around 8°C (46°F) and average highs reaching up to 20°C (68°F), this month presents a comfortable climate perfect for outdoor activities. The average temperature of 14°C (57°F) signals a gradual decline from the warmer months, yet it still offers pleasant days for enjoying the stunning landscapes of the Åland Islands. As the last traces of summer fade, September serves as a delightful prelude to the crisper days ahead, making it a charming time for both locals and visitors alike.
In September, Mariehamn experiences a noticeable shift in precipitation patterns as summer gives way to autumn. With an average rainfall of 56 mm (2.2 in) over 11 days, the month marks a transition to wetter weather compared to the preceding summer months. This increase in rainfall sets the stage for October's even more substantial 90 mm (3.6 in), emphasizing a clear upward trend as the year progresses. As residents and visitors alike prepare for the impending cooler months, September stands out as a bridge, where the lingering warmth of summer meets the more frequent showers of autumn, creating a dynamic shift in the island's climate.
In September, Mariehamn experiences a notable shift in humidity, with levels rising to 85% after the more comfortable summer months. This uptick suggests a transition from the drier conditions of summer—where humidity dipped to as low as 74% in July—toward the more humid autumn and winter seasons, which see figures climbing back to the high 80s and beyond. The gradual increase in humidity throughout the late summer and into September indicates the onset of cooler weather, heralding the approach of autumn while reminding residents of the island's characteristic moisture as winter looms.
As the summer fades into autumn in Mariehamn, Åland Islands, the UV Index experiences a gradual decline. In September, the UV Index stands at 4, indicating a moderate risk of harm from unprotected sun exposure, with an estimated burn time of 30 minutes. This is a slight decrease from the peak summer months of June and July when the Index reached 7. Throughout the month, residents and visitors alike should remain mindful of their sun protection strategies, especially during midday hours. As the seasons change, the need for vigilance against UV rays persists. For more details on UV levels throughout the year, check out the Mariehamn UV Index.
UV Risk Categories
As summer gracefully fades into autumn, September in Mariehamn, Åland Islands offers a delightful balance of sunshine with 318 hours of radiant light. This month's sunshine marks a noticeable decline from the peak brightness of July and June, yet it outshines the earlier months, suggesting a lingering warmth before the onset of chillier days. The gradual tapering of solar hours is a reminder of the shifting seasons, as September stands as a bridge connecting the vibrant days of summer with the softer hues of fall. With each hour of sunshine, the landscape transforms, offering a picturesque backdrop for leisurely strolls and outdoor adventures, making it a perfect time to experience the serene beauty of the Åland Islands.
In Mariehamn, Åland Islands, September marks the transition from the warmth of summer to the cooler days of autumn, and this shift is reflected in the changing likelihood of sunny weather. With a 31% chance of sun, September sits comfortably in the middle of the annual spectrum, showing a notable drop from the peak of 62% in July. While August provides a moderate 39% chance for sunny days, September indicates a slight decline, hinting at the encroaching fall. This trend suggests that while there are still opportunities for pleasant sunshine, visitors should prepare for the possibility of overcast skies as the month unfolds.
As September arrives in Mariehamn, Åland Islands, the days begin to gradually shorten from the summer's peak of 18 hours of daylight in June. By this month, daylight settles at a comfortable 12 hours, providing a gentle transition into fall. Following the vibrant and lengthy days of summer, September offers just enough light to enjoy the beautiful landscapes before the seasons shift. This month marks a notable decrease compared to August's 15 hours, hinting at the approaching autumn while still allowing for plenty of outdoor adventures. As daylight continues to wane in the coming months, the charm of the Åland Islands takes on a new, cozy character.
In September, Mariehamn, nestled in the picturesque Åland Islands, experiences a wind speed of 6.8 m/s (15 mph), maintaining the gentle breezes that have started to emerge since late summer. This month marks a transition, as the winds are reminiscent of August's calm yet begin to hint at the stronger gales of autumn. Following a gradual decline from the robust speeds of winter and early spring, the September winds serve as a pleasant reminder of the changing seasons. As October approaches, residents can expect an uptick to 9.1 m/s (20 mph), foreshadowing the brisk gusts that characterize the later months of the year.
Weather in Mariehamn varies notably across the year, with each month offering distinct climate conditions. This page compares September’s weather to other months in Mariehamn, focusing on differences in temperature, rainfall, humidity, and UV levels.
September and January offer contrasting weather experiences. In September, temperatures range from a mild 8°C (46°F) at night to a comfortable 20°C (68°F) during the day, with an average of 14°C (57°F). The month sees about 56 mm (2.2 in) of precipitation over 11 days, and humidity levels are relatively high at 85%. In stark contrast, January is much colder, with temperatures dropping as low as -8°C (17°F) and averaging around 1°C (35°F), peaking at only 8°C (46°F). Though it experiences slightly less rainfall at 48 mm (1.9 in) over the same number of days, the humidity is higher at 90%, contributing to a more biting chill. For more detailed information on January weather, you can check Mariehamn weather in January.
September and February present starkly contrasting weather conditions. In September, temperatures range from a mild 8°C (46°F) at night to a comfortable 20°C (68°F) during the day, with an average of 14°C (57°F). This month sees about 56 mm (2.2 in) of precipitation over approximately 11 days, coupled with high humidity at 85%. In contrast, February is significantly colder, with temperatures plummeting to a minimum of -10°C (14°F) and only reaching a maximum of 7°C (44°F), resulting in an average temperature of 0°C (33°F). February experiences less rainfall, totaling 38 mm (1.5 in) over 10 days, but the humidity remains high at 88%. For a closer look at February weather specifics, you can check out Mariehamn weather in February.
September and March present contrasting weather conditions in Mariehamn. In September, temperatures are milder, with averages ranging from a minimum of 8°C (46°F) to a maximum of 20°C (68°F), while precipitation is slightly higher at 56 mm (2.2 inches) over 11 rainy days, alongside a humidity level of 85%. In contrast, March is much colder, with temperatures averaging between -10°C (14°F) and 9°C (48°F), and an average precipitation of 37 mm (1.5 inches) over 9 days, accompanied by even higher humidity at 89%. For more details on the weather during this month, visit Mariehamn weather in March.
In comparing the weather between September and April, we find notable differences in temperature and precipitation patterns. September boasts a milder climate, with average temperatures ranging from a minimum of 8°C (46°F) to a maximum of 20°C (68°F) and a total precipitation of 56 mm (2.2 in) over 11 days. In contrast, April experiences chillier conditions, where temperatures range from a minimum of -1°C (30°F) to a maximum of 9°C (48°F) and significantly less precipitation, totaling 24 mm (1.0 in) over just 7 days. Both months have a humidity level of 85%, but the overall cooler temperatures in April make it feel considerably brisker. For more details about April weather in Mariehamn, you can visit Mariehamn weather in April.
When comparing the weather in September and May, September generally offers milder temperatures, with an average of 14°C (57°F) and a maximum of 20°C (68°F), compared to May's cooler average of 7°C (45°F) and maximum of 15°C (59°F). Additionally, September experiences more precipitation, totaling 56 mm (2.2 in) over 11 days, while May has less rainfall at 36 mm (1.4 in) spread over just 6 days. Humidity is also higher in September at 85%, compared to May’s 77%. For more detailed weather information for May, you can visit Mariehamn weather in May.
In comparing the weather of September and June, notable differences emerge in temperature and precipitation. September experiences slightly warmer maximum temperatures, reaching up to 20°C (68°F), while June peaks at 21°C (70°F). Both months have similar minimum temperatures, with September averaging 8°C (46°F) and June at 7°C (44°F). Precipitation is more frequent in September, occurring on 11 days and totaling 56 mm (2.2 in), compared to June's 29 mm (1.1 in) over just 4 days. Additionally, September's humidity is higher at 85%, while June's is more comfortable at 76%. For a more detailed overview of June weather, see Mariehamn weather in June.
In comparing the weather of September and July, it's evident that July tends to be warmer and drier. During July, the average temperature hovers around 17°C (63°F) with maximums reaching up to 24°C (75°F). In contrast, September sees cooler conditions with average temperatures dropping to 14°C (57°F) and highs of only 20°C (68°F). Additionally, July experiences lower humidity at 74% compared to the higher 85% humidity in September. Precipitation is also less prevalent in July, with about 45 mm (1.8 in) over 7 days, whereas September receives about 56 mm (2.2 in) over 11 days. For more detailed information on July weather, you can check Mariehamn weather in July.
In comparing the weather of September to August, September tends to be cooler, with average temperatures dropping from 17°C (63°F) in August to 14°C (57°F). While both months experience similar levels of precipitation—56 mm (2.2 in) in September compared to 53 mm (2.1 in) in August—September sees rainfall spread over 11 days, slightly more than August's 10 days. Additionally, humidity rises significantly in September to 85%, compared to 77% in August, contributing to a more damp atmosphere as summer transitions to autumn. For more details on August weather specifically, check Mariehamn weather in August.
September tends to be milder than October, with average temperatures ranging from a minimum of 8°C (46°F) to a maximum of 20°C (68°F). In contrast, October brings cooler weather, with average temperatures dropping to a minimum of 3°C (37°F) and a maximum of 15°C (59°F). Additionally, October experiences increased precipitation, totaling 90 mm (3.6 in) over 17 days compared to September's 56 mm (2.2 in) over 11 days, and the humidity rises slightly to 89% from September's 85%. For detailed information on what to expect in October, you can visit Mariehamn weather in October.
September and November showcase a notable shift in weather conditions. In September, temperatures begin to cool down with a minimum of 8°C (46°F) and highs reaching up to 20°C (68°F), presenting an average of 14°C (57°F). The month sees 56 mm (2.2 in) of precipitation across 11 days, with an 85% humidity level. In contrast, November significantly lowers temperatures, with minimums dropping to -2°C (29°F) and a maximum of 13°C (55°F), leading to an average of just 6°C (43°F). Precipitation remains roughly similar at 57 mm (2.2 in) over 14 days, while humidity rises to 90%. This stark transition highlights the progression into the colder months. For more detailed insights, take a look at Mariehamn weather in November.
September and December exhibit distinctly different weather patterns in terms of temperature and precipitation. In September, temperatures range from a mild 8°C (46°F) at night to a comfortable 20°C (68°F) during the day, with an average of 14°C (57°F). The month sees about 56 mm (2.2 in) of precipitation over approximately 11 days, and the humidity hovers around 85%. In contrast, December brings a sharp decline in temperatures, with lows of -8°C (19°F) and daytime highs only reaching 7°C (46°F), resulting in an average temperature of just 3°C (37°F). Precipitation increases to 80 mm (3.1 in) spread over 18 days, and humidity rises slightly to 87%. For a more detailed look at December weather, you can visit Mariehamn weather in December.
As September unfolds in Mariehamn, it marks a transition from the warm embrace of summer to the crispness of autumn. Unlike the warmer months, September presents a cooler atmosphere with a notable increase in humidity, wrapping the town in a moist blanket. The sporadic rainfall, often arriving on 11 days, contributes to the month’s characteristic charm, bringing lush greenery and vibrant fall colors. This shift in weather patterns invites both locals and visitors to enjoy the beauty of the season, making it a unique time to explore the island’s landscapes. For a deeper dive into monthly variations, check out Mariehamn Climate.