Last updated: August 23, 2025
In Siuntio, Finland, the average temperature in September hovers around 12°C (54°F). Expect minimums dipping to -1°C (31°F) and maximums soaring to 22°C (73°F). The month sees about 65 mm (2.6 in) of precipitation spread over 13 days, with a high average humidity of 90%. Prepare for a blend of cool breezes and occasional rain!
In September, in Siuntio, the average temperature is 12°C (54°F). The maximum can reach 22°C (73°F), and the minimum can be as low as -1°C (31°F). This makes Siuntio a great destination for travelers looking for mild weather, but it's wise to pack for both warmer days and cooler nights.
In Siuntio in September, the precipitation amount is 65 mm (2.6 in) spread over a duration of 13 days.
In Siuntio in September, humidity is 90%. With an average temperature of 12°C (54°F), this humidity feels like a damp chill that clings to your skin, making outdoor activities uncomfortable and traveling a bit more draining than usual.
In Siuntio in September, the maximum UV index reaches 4, which corresponds to a moderate Exposure Category. With a time to burn of 30 minutes, it’s important to take precautions to protect your skin. You can find more details in the Hourly UV Index in Siuntio for better planning.
UV Risk Categories
Weather in Siuntio varies notably across the year, with each month offering distinct climate conditions. This page compares September’s weather to other months in Siuntio, focusing on differences in temperature, rainfall, humidity, and UV levels.
| Temperature | Precipitation | Humidity | UV | |
|---|---|---|---|---|
| January Weather | -2°C (28°F) | 58 mm (2.3 inches) | 97% | low |
| February Weather | -3°C (26°F) | 49 mm (1.9 inches) | 95% | low |
| March Weather | -1°C (31°F) | 54 mm (2.1 inches) | 93% | moderate |
| April Weather | 3°C (39°F) | 40 mm (1.6 inches) | 86% | moderate |
| May Weather | 10°C (50°F) | 53 mm (2.1 inches) | 75% | moderate |
| June Weather | 16°C (61°F) | 51 mm (2.0 inches) | 75% | high |
| July Weather | 18°C (64°F) | 83 mm (3.3 inches) | 80% | high |
| August Weather | 16°C (62°F) | 78 mm (3.1 inches) | 83% | moderate |
| September Weather | 12°C (54°F) | 65 mm (2.6 inches) | 90% | moderate |
| October Weather | 7°C (45°F) | 88 mm (3.5 inches) | 93% | low |
| November Weather | 3°C (38°F) | 63 mm (2.5 inches) | 94% | low |
| December Weather | -1°C (31°F) | 75 mm (2.9 inches) | 95% | low |