September Weather in Koya, Japan

Last updated: August 23, 2025

In September, the average temperature in Koya, Japan reaches a comfortable 24°C (75°F). However, be prepared for a range, with nighttime lows dipping to a chilly 12°C (54°F) and daytime highs soaring to 34°C (94°F). Expect 204 mm (8.0 in) of precipitation spread over 16 days, contributing to a notably high average humidity of 87%.

September Temperature in Koya

In September in Koya, the average temperature is 24°C (75°F). Maximums can reach 34°C (94°F), while minimums can go as low as 12°C (54°F). It's a great time to explore outdoor activities and enjoy pleasant weather.

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

The chart illustrates September temperature patterns in Koya, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Koya, September typically has an average temperature of 24°C (75°F), with highs reaching up to 34°C (94°F) and lows dropping to around 12°C (54°F).

Data source: Temperature data for Koya generated using information from the Copernicus Climate Change Service.

September Precipitation in Koya

In Koya in September, the precipitation amount is 204 mm (8.0 in) spread over 16 days.

September Precipitation Trends in Koya

The chart displays monthly precipitation patterns in Koya, 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 Koya, September typically receives around 204 mm (8.0 inches) of precipitation spread over approximately 16 days.

Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.

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Millimeters (mm) Inches (in)

September Humidity in Koya

In Koya in September, humidity is 87%. With an average temperature of 24°C (75°F), this humidity feels like a warm, sticky embrace that clings to your skin, making outdoor activities feel heavier and more exhausting, and the air thickens, leaving you longing for shade and refreshing breezes as you navigate your adventures.

September Average Humidity in Koya

This chart illustrates the average monthly humidity levels in Koya, 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 Koya is approximately 87%, offering insight into how humid the weather typically is during this month.

Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in Koya

In Koya in September, the maximum UV index reaches 10, which corresponds to a very high Exposure Category. With a time to burn of just 15 minutes, it's crucial to take precautions. For more detailed information, you can check the Hourly UV Index in Koya.

Maximum UV Index Levels in Koya for September

The chart shows the monthly maximum UV Index (UVI) for Koya 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 Koya typically reaches 10, which falls under the very high exposure category.

Data source: Koya 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 Koya Compares to Other Months

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

This table compares monthly weather conditions in Koya, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
	Temperature	Precipitation	Humidity	UV
January Weather	4°C (40°F)	67 mm (2.6 inches)	82%	moderate
February Weather	5°C (41°F)	83 mm (3.3 inches)	79%	high
March Weather	9°C (49°F)	127 mm (5.0 inches)	74%	very high
April Weather	14°C (57°F)	132 mm (5.2 inches)	76%	extreme
May Weather	19°C (66°F)	169 mm (6.7 inches)	83%	extreme
June Weather	22°C (72°F)	220 mm (8.7 inches)	87%	extreme
July Weather	26°C (79°F)	324 mm (12.7 inches)	93%	extreme
August Weather	28°C (82°F)	203 mm (8.0 inches)	91%	extreme
September Weather	24°C (75°F)	204 mm (8.0 inches)	87%	very high
October Weather	18°C (65°F)	265 mm (10.5 inches)	85%	high
November Weather	12°C (54°F)	62 mm (2.4 inches)	83%	high
December Weather	7°C (44°F)	79 mm (3.1 inches)	83%	moderate