Iiyama Monthly Rainfall & Precipitation
This page shows both the average monthly rainfall and the number of rainy days in Iiyama, Nagano Prefecture, Japan. These values are calculated using 30 years of data (1990–2020) to ensure accuracy. Now, let's explore all the details to give you a full picture.
Iiyama is known for its substantial rain/snowfall, with annual precipitation reaching 2163 mm (85 in). While the overall climate is wet, there are notable seasonal patterns that create interesting contrasts, as demonstrated in our graph below.
Monthly Precipitation Levels
The average number of days each month with precipitation (> 0.2 mm (0.01 in))
Iiyama offers a pleasant mix of wetter and slightly drier months. The difference in precipitation between July (257 mm (10 in)) and April (126 mm (5 in)) is not too significant, making the climate enjoyable for visitors and residents alike.
July, the wettest month, has a maximum daytime temperature of 28°C (82°F). The city receives 154 hours of sunshine in this period. During the driest month April you can expect a temperature of 14°C (57°F). For more detailed insights into the city's temperatures, visit our Iiyama Temperature page.
Daily Historical Precipitation
49-year average (1976-2025)
Average daily rainfall for each day of the month based on long-term records.
Average precipitation in July
Explore Iiyama's Historical Precipitation: 1976-2026
Browse day-by-day precipitation records for Iiyama spanning 51 years. Select any month and year to see actual rainfall and snowfall recorded on each day.
Annual Rainfall in Japan: City Comparison
The map below shows the annual precipitation across Japan. You can also select the different months in case you are interested in a specific month.
heavy rainfall
high
moderate
low
almost none
Iiyama vs World: Rainfall Compared
Iiyama's average annual precipitation is 2163 mm (85 in). Let's compare this to some popular worldwide tourist destinations:
Boston, USA, experiences 1238 mm (49 in) of annual precipitation, including significant snowfall during the winter.
Meanwhile, Buenos Aires, Argentina, enjoys a humid subtropical climate with 1000 mm (39 in) of annual rainfall, mostly in the summer.
In Tokyo, Japan, the average annual precipitation is 1528 mm (60 in), with significant summer rains due to typhoon season.
Singapore, situated near the equator, gets 2581 mm (102 in) of rainfall annually, with no distinct dry season and consistent monthly precipitation.
Precipitation amounts are measured using specific gauges installed at weather stations, collecting both rain and snow and any other type of precipitation. Rainfall is measured directly in millimeters, while that from snow and ice is obtained by melting it. Automated systems often incorporate heaters to make this easier.
Information from these stations is transmitted via Wi-Fi, satellite, GPS, or telephone connections to central monitoring networks. This information is immediately updated and integrated into weather models and forecasts.
- The U.S. has a significant number of thunderstorms every year, with over 14.6 million taking place across the world annually.
- Approximately 70% of lightning bolts strike land rather than oceans.
- A storm named John was the longest-lasting Pacific tropical storm, continuing for 31 days. As it crossed the dateline twice, it changed status from a hurricane to a typhoon and back to a hurricane.
For more detailed information about Iiyama's weather, including sunshine hours, humidity levels, and temperature data, visit our Iiyama Climate page.
