O'Fallon (MO) Rainfall & Precipitation: Monthly Averages and Year-Round Insights

This page shows the average amount of rainfall per month in O'Fallon (MO). The numbers are calculated over a 30-year period to provide a reliable average. Let’s explore the details in depth to provide you with a complete overview.

O'Fallon experiences significant rain/snowfall throughout the year, averaging 1086 mm of precipitation annually.

Monthly Precipitation Levels

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

O'Fallon can be quite wet during June, receiving approximately 119 mm of precipitation over 12 rainy days.

In contrast January, experiences much drier conditions, with 44 mm of snow/rainfall, spread across 7 snowy/rainy days.

June, the city’s wettest month, has a maximum daytime temperature of 30°C. During the driest month January you can expect a temperature of 5°C. For more detailed insights into the city’s temperatures, visit our O'Fallon 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

O'Fallon’s average annual precipitation is 1086 mm. Let’s compare this to some popular worldwide tourist destinations:

In Toronto, Canada, annual precipitation averages [964 mm], with snowy winters and rainy summers.

In Shanghai, China, the annual average precipitation is 1347 mm, with a humid subtropical climate.

Adelaide, Australia, enjoys 511 mm of annual precipitation, with dry summers and wet winters.

Singapore, situated near the equator, gets 2581 mm of rainfall annually, with no distinct dry season and consistent monthly precipitation.

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.

Interesting weather facts

• "Ginger" was the longest-lasting Atlantic tropical storm, which spun around the open ocean for 28 days in 1971.
• The world's largest snowflake was recorded in the Guinness Book of Records, at 38 cm wide and 20 cm thick. The snowflake fell at Fort Keogh, Montana, USA, on 28 January 1887.
• The greatest snowfall recorded was on Mt. Rainier, Washington State, USA—over 31.5 meters fell during the winter of 1972.

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