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September Weather in Isojoki, Finland

Last updated: August 23, 2025

In September, the average temperature in Isojoki, Finland hovers around 11°C (51°F), with daily variations that can dip to a brisk -2°C (29°F) or rise to a pleasant 24°C (76°F). Be prepared for some rain, as 77 mm (3.0 in) of precipitation typically falls over 12 days, accompanied by an average humidity level of 86%. Whether you’re layering up or enjoying mild afternoons, don't forget to embrace the charm of the season!

September Temperature in Isojoki

In September in Isojoki, the average temperature is 11°C (51°F). The maximum can reach 24°C (76°F), while the minimum can be as low as -2°C (29°F). This varied climate makes it a perfect time for travelers to pack layers and enjoy outdoor activities in Isojoki.

September Weather in Isojoki: Daily Temperature Highs, Lows, and Averages

The chart illustrates September temperature patterns in Isojoki, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Isojoki, September typically has an average temperature of 11°C (51°F), with highs reaching up to 24°C (76°F) and lows dropping to around -2°C (29°F).
JanFebMarAprMayJunJulAugSepOctNovDec252329384960635951423528
Data source: Temperature data for Isojoki generated using information from the Copernicus Climate Change Service.
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The average of daily temperatures (24 hours) calculated across all days in the month.

September Precipitation in Isojoki

In Isojoki in September, the precipitation amount is 77 mm (3.0 in) spread over 12 days.

September Precipitation Trends in Isojoki

The chart displays monthly precipitation patterns in Isojoki, with values for each month alongside September’s data, which is highlighted for easy comparison. It shows the amount of precipitation, providing insights into how September’s conditions compare to those of other months. In Isojoki, September typically receives around 77 mm (3.0 inches) of precipitation spread over approximately 12 days.
JanFebMarAprMayJunJulAugSepOctNovDec4346484647698711377806867
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in Isojoki

In Isojoki in September humidity is 86%. With an average temperature of 11°C (51°F), this humidity feels like a damp blanket wrapping around you, making outdoor activities less enjoyable and travel a bit more strenuous as the air feels heavy and clammy.

September Average Humidity in Isojoki

This chart illustrates the average monthly humidity levels in Isojoki, with September’s data highlighted for easy comparison. It shows the fluctuation in humidity throughout the year, helping you understand how conditions vary by season. In September, average humidity in Isojoki is approximately 86%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec92%90%89%85%77%78%78%79%86%90%91%89%
Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in Isojoki

In Isojoki in September, the maximum UV index is 3, which corresponds to a moderate Exposure Category. The time to burn is approximately 30 minutes. For more details on the hourly UV index in Isojoki, you can check the information here.

Maximum UV Index Levels in Isojoki for September

The chart shows the monthly maximum UV Index (UVI) for Isojoki in September, representing the highest UV radiation level. The UVI measures the intensity of ultraviolet radiation from the sun, indicating the potential risk of sunburn and UV-related health issues. In September, the maximum UV index in Isojoki typically reaches 3, which falls under the moderate exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec113456653211
Data source: Isojoki September UVI data generated using information from the Copernicus Climate Change Service.

UV Risk Categories

  •  Extreme (11+): Avoid the sun, stay in shade.
  •  Very High (8-10): Limit sun exposure.
  •  High (6-7): Use SPF 30+ and protective clothing.
  •  Moderate (3-5): Midday shade recommended.
  •  Low (0-2): No protection needed.

How September Weather in Isojoki Compares to Other Months

Weather in Isojoki varies notably across the year, with each month offering distinct climate conditions. This page compares September’s weather to other months in Isojoki, focusing on differences in temperature, rainfall, humidity, and UV levels.

This table compares monthly weather conditions in Isojoki, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather-4°C (26°F)43 mm (1.7 inches)92%low
February Weather-5°C (24°F)46 mm (1.8 inches)90%low
March Weather-2°C (29°F)48 mm (1.9 inches)89%moderate
April Weather3°C (38°F)46 mm (1.8 inches)85%moderate
May Weather9°C (49°F)47 mm (1.8 inches)77%moderate
June Weather16°C (61°F)69 mm (2.7 inches)78%high
July Weather17°C (63°F)87 mm (3.4 inches)78%high
August Weather15°C (60°F)113 mm (4.5 inches)79%moderate
September Weather11°C (51°F)77 mm (3.0 inches)86%moderate
October Weather6°C (42°F)80 mm (3.1 inches)90%low
November Weather2°C (35°F)68 mm (2.7 inches)91%low
December Weather-2°C (29°F)67 mm (2.6 inches)89%low

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