Alton (IL) Rainfall & Precipitation: Monthly Averages and Year-Round Insights

This page shows the average amount of rainfall per month in Alton (IL). The numbers are calculated over a 30-year period to provide a reliable average. Let's now guide you through the details for a complete overview.

Alton has a notably wet climate with abundant precipitation, recording 1007 mm of rain/snowfall per year.

Monthly Precipitation Levels

The average number of days each month with precipitation (> 0.2 mm)

The seasons in Alton, bring significant changes in precipitation. The wettest month, April, receives high rainfall, with an average of 115 mm of precipitation.

This rainfall is distributed across 11 rainy days. In contrast, the driest month, January, experiences much less snow/rainfall, totaling 42 mm over 7 snowy/rainy days. These distinct seasonal differences provide diverse experiences throughout the year.

April, the city’s wettest month, has a maximum daytime temperature of 19°C and receives 225 hours of sunshine. During the driest month January you can expect a temperature of 4°C. For more detailed insights into the city’s temperatures, visit our Alton Temperature page.

Annual Precipitation in the United States of America

The map below shows the annual precipitation across the United States of America. You can also select the different months in case you are interested in a specific month.

Amsterdam Precipitation Compared World Wide

Alton’s average annual precipitation is 1007 mm. Let’s compare this to some popular worldwide tourist destinations:

The city of Rome, Italy, has an average annual precipitation of 832 mm, spread fairly evenly throughout the year.

Osaka, Japan, experiences 1507 mm of rainfall annually, spread across the year with wetter summers.

In Tokyo, Japan, the average annual precipitation is 1528 mm, with significant summer rains due to typhoon season.

Ho Chi Minh City, Vietnam, receives 1955 mm of annual rainfall, with a pronounced wet season from May to November, typical of its tropical monsoon climate.

How is Precipitation Measured?

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.

How Does Precipitation Affect Local Climate?

Precipitation has a very strong role in determining the local climate and ecosystem:

• Rainy Seasons: Many parts of the world have well-defined wet seasons where precipitation is distinctly higher. These are normally accompanied by lush vegetation and temperature patterns.
• Dry Seasons: In areas where the climate is either desert or Mediterranean, the amount of precipitation is drastically reduced, leading to a shortage of water and arid conditions.

For more detailed information about Alton (IL)’s weather, including sunshine hours, humidity levels, and temperature data, visit our Alton (IL) Climate page.