Climate Overview
The climate in Iiyama is temperate. The average annual temperature is 11°C and approximately 1823mm of precipitation falls per year. Iiyama receives a notable amount of rainfall throughout the year, including during its driest month. Iiyama is in the Northern Hemisphere. Summer begins at the end of June and lasts through September. The summer months are: August, July, September. The coldest months are January, February, December, when temperatures can drop to -5°C. Iiyama experiences heavy snowfall, typically from January through December.
Temperature
Temperatures in Iiyama vary considerably across the year, with a 33°C difference between the coldest and warmest months. The warmest month is August, when average highs reach 28°C and the mean temperature sits around 23°C. The coldest month is January, when overnight lows fall to -5°C and the daily average is -1°C. Daily temperature variation is modest, with an average difference of 8°C between highs and lows. The sharpest temperature change occurs between April and May, with a 7°C shift in average temperatures.
Precipitation
Iiyama is a fairly wet location, receiving approximately 1823mm of precipitation annually, which averages out to around 152mm per month. The wettest month is July, averaging 282mm of rainfall. October and September also tend to see above-average precipitation. The driest month is November, with just 80mm. That's 202mm less than July, the wettest month. Precipitation varies noticeably between seasons, with the second half (July to December) of the year generally seeing more rainfall. Iiyama receives heavy snowfall, accumulating around 335cm annually from January through December. The snowiest month is January, with approximately 109cm. Winter travel should account for significant snow cover.
Wind
Iiyama is relatively calm, with an average annual wind speed of 2km/h. For context, sustained winds below 12km/h are generally light, while anything above 25km/h is considered strong. The windiest month is April, averaging 2km/h, though still comfortable for most outdoor activities. The calmest conditions occur in July, with average winds dropping to 1km/h, making it an ideal period for wind-sensitive activities. There is moderate seasonal variation in wind speed, with a 1km/h gap between the calmest and windiest months.
Seasons
93 days until Autumn
It is currently summer in Iiyama, which began on June 21, 2026. Iiyama is in the Northern Hemisphere, where spring begins in March, summer in June, autumn in September, and winter in December. The warmest period peaks in August at around 28°C, while the coldest stretch bottoms out in January near -5°C. Autumn is next, beginning on September 23, 2026 — 93 days from now.
Spring
Temperatures range from -1 to 21°C. Rainfall is heavy, totalling around 365mm across the season with a monthly average of 122mm. Winds are generally light, averaging 2km/h. An umbrella or waterproof jacket is advisable as spring showers are frequent.
Summer
Temperatures range from 14 to 28°C. Rainfall is heavy, totalling around 632mm across the season with a monthly average of 211mm. Winds are generally light, averaging 1km/h. Light, breathable clothing is ideal — perfect conditions for outdoor activities.
Autumn
Temperatures range from 3 to 23°C. Rainfall is heavy, totalling around 476mm across the season with a monthly average of 159mm. Expect around 15cm of snow accumulation during this period. Winds are generally light, averaging 2km/h. A waterproof jacket and sturdy footwear are recommended as rain becomes more frequent.
Winter
Temperatures range from -5 to 5°C. Rainfall is heavy, totalling around 351mm across the season with a monthly average of 117mm. Expect around 243cm of snow accumulation during this period. Winds are generally light, averaging 2km/h. Warm winter clothing and waterproof boots are a must, and travel may be affected by snow.
Monthly Climate Data
The table below shows monthly climate averages for Iiyama based on historical weather data. Min and max temperatures represent typical overnight lows and afternoon highs for each month, shown in degrees Celsius (°C). Precipitation is measured in millimetres (mm) and indicates the average total rainfall per month. Snow is measured in centimetres (cm) and reflects average monthly snowfall accumulation. Wind speed is the average sustained speed in kilometres per hour (km/h). All values are based on averages from over 10 years of historical weather data. The current month is highlighted for quick reference.
