Climate of O’Fallon, Missouri

by | December 24, 2023

O’Fallon, Missouri, is a thriving city located in St. Charles County in the eastern part of the state. As one of the fastest-growing cities in Missouri, O’Fallon combines suburban charm with a growing community and a diverse range of amenities. To understand the weather and climate of O’Fallon, it’s essential to explore its seasonal variations, precipitation patterns, temperature ranges, and the influence of its geographical location.

Geography and Location:

According to Citiesplustowns, O’Fallon is situated in St. Charles County, Missouri, approximately 35 miles west of downtown St. Louis. The city is part of the St. Louis metropolitan area and has experienced significant population growth in recent decades. The city’s location in the central part of the United States contributes to its climate, which is influenced by continental air masses.

Climate Classification:

O’Fallon falls under the classification of a humid continental climate. This climate type is characterized by four distinct seasons, with warm to hot summers, cold winters, and noticeable variations in temperature between seasons. The absence of significant geographic features like large bodies of water or mountains means that O’Fallon experiences a more continental climate with temperature extremes.


  1. Spring:

Spring in O’Fallon typically begins in March and extends through May. During this season, the city experiences a gradual warming, with average temperatures ranging from the 40s°F (4–9°C) in March to the 60s and 70s°F (15–26°C) in May. Spring is marked by the blossoming of trees and flowers, and residents often engage in outdoor activities as the weather becomes more inviting.

  1. Summer:

O’Fallon’s summers, from June to August, are warm to hot. Average temperatures range from the 70s°F (21–26°C) in June to the 80s and occasionally 90s°F (27–37°C) in July and August. Humidity levels can be moderate to high, and the summer months often bring occasional thunderstorms. Summer is a popular time for outdoor recreation, community events, and enjoying the city’s parks and green spaces.

  1. Autumn:

Fall in O’Fallon, spanning from September to November, sees a gradual cooling of temperatures and the changing of foliage. Average temperatures range from the 60s°F (15–21°C) in September to the 40s°F (4–9°C) in November. Fall foliage becomes a prominent feature, attracting residents and visitors alike to enjoy the scenic beauty of O’Fallon and its surroundings.

  1. Winter:

Winters in O’Fallon, from December to February, are cold. Average temperatures range from the 30s°F (around 0°C) in December and January to the 40s°F (4–9°C) in February. While snowfall is not as frequent or abundant as in more northern climates, the city may experience occasional snow and frost. Winter activities are limited, but the colder climate allows for seasonal festivities and indoor attractions.


O’Fallon receives a moderate amount of precipitation throughout the year, with an average annual rainfall of about 40 inches (1016 mm). Precipitation is relatively evenly distributed across the seasons, although the summer months may see slightly higher amounts due to the occurrence of thunderstorms. Snowfall is typically modest, and the city experiences a mix of rain and snow during the colder months.

Influence of Continental Climate:

O’Fallon’s climate is influenced by its central location within the continental United States. The absence of large bodies of water means that the city experiences more significant temperature variations between seasons. Summers can be warm to hot, and winters bring colder temperatures. The continental climate contributes to the characteristic weather patterns observed in O’Fallon.


O’Fallon may exhibit microclimates within its borders due to variations in elevation, proximity to water bodies, and urban versus suburban settings. Areas near the Missouri River or local lakes may experience slightly different temperature and humidity levels compared to more urbanized sections of the city. These microclimatic variations contribute to the diversity of experiences within O’Fallon.

Climate Change Considerations:

O’Fallon, like many communities worldwide, faces considerations related to climate change. Changes in temperature, precipitation patterns, and the potential for more extreme weather events are areas of concern. The city may be engaged in climate resilience planning, focusing on sustainable practices and infrastructure improvements to address these challenges.


O’Fallon, Missouri, boasts a humid continental climate characterized by its four distinct seasons. With a mix of suburban landscapes, growing communities, and recreational opportunities, residents and visitors can enjoy a diverse range of experiences throughout the year. The city’s proximity to St. Louis, coupled with its local amenities, makes O’Fallon an attractive place to live and visit. As O’Fallon continues to evolve, its climate remains a defining aspect, shaping the lifestyle and experiences of those who call it home.

O'Fallon, Missouri