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September Weather in Koshimizu, Japan

Last updated: August 23, 2025

In September, the average temperature in Koshimizu, Japan hovers around 16°C (61°F), with minimums dipping to 5°C (42°F) and reaching maximums of 29°C (84°F). Expect a total precipitation of 95 mm (3.7 in) spread over approximately 12 days, contributing to a high average humidity of 89%.

September Temperature in Koshimizu

In September in Koshimizu, the average temperature is 16°C (61°F). The maximum can reach 29°C (84°F), while the minimum can drop as low as 5°C (42°F). This makes it an ideal time for travelers to enjoy a diverse range of outdoor activities, from warm afternoons to cooler evenings.

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

The chart illustrates September temperature patterns in Koshimizu, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Koshimizu, September typically has an average temperature of 16°C (61°F), with highs reaching up to 29°C (84°F) and lows dropping to around 5°C (42°F).
JanFebMarAprMayJunJulAugSepOctNovDec191828395056646561513926
Data source: Temperature data for Koshimizu 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 Koshimizu

In Koshimizu in September, the precipitation amount is 95 mm (3.7 in) over the course of 12 days.

September Precipitation Trends in Koshimizu

The chart displays monthly precipitation patterns in Koshimizu, 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 Koshimizu, September typically receives around 95 mm (3.7 inches) of precipitation spread over approximately 12 days.
JanFebMarAprMayJunJulAugSepOctNovDec54558872959679129951599670
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in Koshimizu

In Koshimizu in September, humidity is 89%. With an average temperature of 16°C (61°F), this humidity feels like a heavy blanket enveloping you, making outdoor activities feel sluggish and sticky, which can be quite challenging for travelers looking to explore.

September Average Humidity in Koshimizu

This chart illustrates the average monthly humidity levels in Koshimizu, 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 Koshimizu is approximately 89%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec84%83%83%83%86%88%93%96%89%83%80%79%
Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in Koshimizu

In Koshimizu in September, the maximum UV index is 8, which corresponds to a very high Exposure Category. This means that the time to burn is only 15 minutes. For more detailed information, you can refer to the Hourly UV Index in Koshimizu.

Maximum UV Index Levels in Koshimizu for September

The chart shows the monthly maximum UV Index (UVI) for Koshimizu 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 Koshimizu typically reaches 8, which falls under the very high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec2367891098532
Data source: Koshimizu 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 Koshimizu Compares to Other Months

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

This table compares monthly weather conditions in Koshimizu, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather-7°C (19°F)54 mm (2.1 inches)84%low
February Weather-8°C (19°F)55 mm (2.2 inches)83%moderate
March Weather-2°C (29°F)88 mm (3.5 inches)83%high
April Weather4°C (39°F)72 mm (2.8 inches)83%high
May Weather10°C (50°F)95 mm (3.7 inches)86%very high
June Weather13°C (56°F)96 mm (3.8 inches)88%very high
July Weather18°C (64°F)79 mm (3.1 inches)93%very high
August Weather18°C (65°F)129 mm (5.1 inches)96%very high
September Weather16°C (61°F)95 mm (3.7 inches)89%very high
October Weather11°C (51°F)159 mm (6.2 inches)83%moderate
November Weather4°C (40°F)96 mm (3.8 inches)80%moderate
December Weather-3°C (27°F)70 mm (2.8 inches)79%low

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