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

This page shows both the average monthly rainfall and the number of rainy days in Chicago, Illinois, United States of America. Long-term data from 1990 to 2020 was used to calculate these averages. Now, let’s explore all the details to give you a full picture.

Chicago is known for its substantial rain/snowfall, with annual precipitation reaching 1062 mm.

Monthly Precipitation Levels

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

Significant seasonal changes in precipitation occur throughout the year. During the wet season, June receives substantial rainfall, averaging 126 mm of precipitation, recorded across 14 rainy days.

In contrast, the drier season, January brings less snowfall, with 50 mm over 10 snowy days.

June, the wettest month, has a maximum daytime temperature of 26°C. The city receives 311 hours of sunshine in this period. During the driest month January you can expect a temperature of -1°C. For more detailed insights into the city’s temperatures, visit our Chicago 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

Chicago’s average annual precipitation is 1062 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.

In Seoul, South Korea, the average annual precipitation is 1237 mm, with most rain falling during the summer monsoon season.

In Brisbane, Australia, the annual precipitation is 979 mm, making it wetter than Sydney.

Bangkok, Thailand, experiences a tropical monsoon climate with 1668 mm of annual rainfall, with the heaviest precipitation occurring during September and October.

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.

Global Precipitation Patterns

Tropical Rainforests: In tropical regions, rainfall is generally abundant year-round. Areas near the equator, like the Amazon rainforest, can receive up to 3000 mm of rain annually.

Desert Regions: Deserts such as the Sahara and Arabian deserts typically see less than 250 mm of rainfall annually. Rainfall tends to be infrequent, but when it does occur, it is often intense.

Temperate Zones: In temperate regions, precipitation tends to be more evenly distributed, though areas closer to the ocean may see more rain in the winter months, and areas further inland experience drier summers.

Polar Regions: Precipitation in polar regions, like Antarctica, is extremely low, often falling as snow. Average annual precipitation in Antarctica is less than 200 mm, with some areas receiving as little as 50 mm annually.

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