September Weather in Iiyama, Japan

Last updated: August 23, 2025

In September, the average temperature in Iiyama, Japan is a pleasant 19°C (67°F), with a minimum of 7°C (44°F) and a maximum reaching 32°C (89°F). Be prepared for some rain, as 194 mm (7.6 in) of precipitation is expected over 19 days, contributing to the high average humidity of 89%. Plan your activities accordingly!

September Temperature in Iiyama

In September in Iiyama, the average temperature is 19°C (67°F). Maximum temperatures can reach 32°C (89°F), while the minimum can drop as low as 7°C (44°F). It's a great time to visit for those who enjoy mild weather and pleasant days, but be prepared for cooler evenings.

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

The chart illustrates September temperature patterns in Iiyama, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Iiyama, September typically has an average temperature of 19°C (67°F), with highs reaching up to 32°C (89°F) and lows dropping to around 7°C (44°F).

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

September Precipitation in Iiyama

In Iiyama in September, the total precipitation amount is 194 mm (7.6 in) recorded over a span of 19 days.

September Precipitation Trends in Iiyama

The chart displays monthly precipitation patterns in Iiyama, 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 Iiyama, September typically receives around 194 mm (7.6 inches) of precipitation spread over approximately 19 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 Iiyama

In Iiyama in September, humidity is 89%. With an average temperature of 19°C (67°F), this humidity feels like a warm, muggy blanket enveloping you, making outdoor activities uncomfortable and encouraging travelers to seek shaded areas or indoor attractions during the hottest parts of the day.

September Average Humidity in Iiyama

This chart illustrates the average monthly humidity levels in Iiyama, 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 Iiyama is approximately 89%, 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 Iiyama

In Iiyama 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 Iiyama.

Maximum UV Index Levels in Iiyama for September

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

Data source: Iiyama 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 Iiyama Compares to Other Months

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

This table compares monthly weather conditions in Iiyama, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
	Temperature	Precipitation	Humidity	UV
January Weather	-2°C (29°F)	144 mm (5.7 inches)	88%	moderate
February Weather	-1°C (30°F)	129 mm (5.1 inches)	86%	high
March Weather	4°C (39°F)	133 mm (5.2 inches)	81%	very high
April Weather	9°C (48°F)	141 mm (5.5 inches)	78%	very high
May Weather	15°C (59°F)	160 mm (6.3 inches)	81%	extreme
June Weather	18°C (65°F)	171 mm (6.7 inches)	88%	extreme
July Weather	22°C (73°F)	341 mm (13.4 inches)	92%	extreme
August Weather	24°C (75°F)	198 mm (7.8 inches)	92%	extreme
September Weather	19°C (67°F)	194 mm (7.6 inches)	89%	very high
October Weather	13°C (56°F)	217 mm (8.5 inches)	87%	high
November Weather	7°C (44°F)	94 mm (3.7 inches)	85%	moderate
December Weather	1°C (34°F)	151 mm (6.0 inches)	86%	moderate