O'Fallon in Spring
In spring (March, April and May), O'Fallon sees average daytime highs around 66°F and overnight lows near 48°F, with 13.8 in of precipitation over about 36 wet days across the season. It is the 3rd-warmest season and the wettest season of the year.
Over the season highs climb from about 51°F in early March to 80°F by late May. The sky is clear or mostly clear about 29% of the time across spring, and the air most often feels dry.
Spring is O'Fallon's 2nd-best season to visit on our travel score. For the whole year in context, see O'Fallon's year-round climate.
- Avg daytime high
- 66°F
- 3rd-warmest season
- Avg overnight low
- 48°F
- Precipitation
- 13.8 in
- 36 wet days
- Avg wind
- 8 mph
- Travel score
- 5.3
- 2nd-best season
- Months
- Mar · Apr · May
Temperature in O'Fallon in Spring
Over the season highs climb from about 51°F in early March to 80°F by late May.
A typical spring day in O'Fallon reaches about 66°F and drops to 48°F overnight. The warmest of the three months is May, the coolest March.
How spring really feels in O'Fallon
Once humidity and wind are folded in, spring brings about 0 days that feel above 90°F and 15 that feel at or below 32°F.
The story in spring is cold — wind chill drags the overnight "feels like" below the raw low.
O'Fallon weather by month
How the three spring months (March, April and May) compare with the rest of the year — the season's months are highlighted.
| Month | High / Low (°F) | Rainfall (inches) | Wet days | Snow days | Daylight (hours) | Travel score |
|---|---|---|---|---|---|---|
| Jan | 40° / 25° | 2.9 | 8.3 | 2.9 | 9.6 | 0.0 |
| Feb | 45° / 29° | 2.6 | 7.6 | 2.6 | 10.5 | 1.0 |
| Mar | 56° / 38° | 3.8 | 10.8 | 1.3 | 11.7 | 3.7 |
| Apr | 67° / 48° | 4.8 | 11.5 | 0.1 | 13 | 5.9 |
| May | 76° / 58° | 5.1 | 13.3 | 0 | 14.1 | 6.3 |
| Jun | 85° / 67° | 4.1 | 10.8 | 0 | 14.6 | 5.2 |
| Jul | 88° / 71° | 3.4 | 9.8 | 0 | 14.4 | 4.6 |
| Aug | 86° / 68° | 2.9 | 9.1 | 0 | 13.5 | 5.1 |
| Sep | 80° / 60° | 3.2 | 7.6 | 0 | 12.3 | 7.0 |
| Oct | 68° / 49° | 3.5 | 8.4 | 0 | 11 | 6.7 |
| Nov | 55° / 38° | 3.7 | 8.7 | 0.6 | 9.9 | 3.6 |
| Dec | 44° / 29° | 2.8 | 8.5 | 2 | 9.4 | 0.7 |
Cloud cover in Spring
The sky is clear or mostly clear about 29% of the time across spring.
Chance of precipitation in Spring
O'Fallon gets around 13.8 in of rain and snow over 36 wet days across spring. The line is the day-by-day chance of measurable precipitation.
Humidity in Spring
Most of spring feels dry — the stacked bands show each day's mix of comfort levels, read off the dew point.
Wind in Spring
Winds average 8 mph across spring.
Sunrise & sunset in Spring
Daylight runs from about 11 h 06 min in early March to 14 h 30 min by late May. The lit band spans sunrise to sunset each day.
Solar energy in Spring
Average shortwave solar energy reaching the ground each day across spring, about 5.0 kWh/m².
Is spring a good time to visit O'Fallon?
Our two travel scores rate spring for general sightseeing and for beach or pool weather — 0 (poor) to 10 (ideal), averaged across the three months.
spring is a reasonable time to visit O'Fallon for sightseeing.
What to pack for O'Fallon in Spring
From spring's temperature range, rain chance, sun and wind — what's worth putting in the bag.
In spring, O'Fallon sees daytime highs around 66°F and nights near 48°F. Worth packing: light clothes, a warm layer, rain gear and sun protection. About 36 days see rain.
UV index in O'Fallon in Spring
Clear-sky midday UV across spring averages around 7 — enough to warrant sun protection. The full-year curve, shaded by WHO exposure level, is below.
Under clear skies, the midday UV index in O'Fallon peaks around June 22 at about 9 (very high) — sunscreen, a hat and midday shade are essential. It bottoms out near December 23 at about 2 (moderate).
The index reaches 3 or more — the level where the WHO recommends sun protection — in 10 months of the year.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| UV index (midday) | 2 | 3 | 5 | 7 | 8 | 9 | 9 | 8 | 7 | 4 | 3 | 2 |
| Level | Moderate | Moderate | High | High | Very high | Very high | Very high | Very high | High | Moderate | Moderate | Low |
| UV index (midday) | Level | |
|---|---|---|
| Jan | 2 | Moderate |
| Feb | 3 | Moderate |
| Mar | 5 | High |
| Apr | 7 | High |
| May | 8 | Very high |
| Jun | 9 | Very high |
| Jul | 9 | Very high |
| Aug | 8 | Very high |
| Sep | 7 | High |
| Oct | 4 | Moderate |
| Nov | 3 | Moderate |
| Dec | 2 | Low |
Air quality in O'Fallon in Spring
Average fine-particle pollution (PM2.5) through the year — so you can see where spring falls, not just the annual average.
Air quality in O'Fallon is worst in July — around 18 µg/m³ PM2.5 (moderate), about 2.3× the cleanest month (October, 8 µg/m³).
Modeled monthly averages (CAMS reanalysis, 2015–2024).
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| PM2.5 (µg/m³) | 9 | 12 | 12 | 11 | 14 | 16 | 18 | 15 | 12 | 8 | 8 | 9 |
| Level | Good | Good | Good | Good | Moderate | Moderate | Moderate | Moderate | Moderate | Good | Good | Good |
| PM2.5 (µg/m³) | Level | |
|---|---|---|
| Jan | 9 | Good |
| Feb | 12 | Good |
| Mar | 12 | Good |
| Apr | 11 | Good |
| May | 14 | Moderate |
| Jun | 16 | Moderate |
| Jul | 18 | Moderate |
| Aug | 15 | Moderate |
| Sep | 12 | Moderate |
| Oct | 8 | Good |
| Nov | 8 | Good |
| Dec | 9 | Good |
Where is O'Fallon?
O'Fallon sits at 38.6°N, 89.9°W, 548 ft above sea level, in United States. The nearest listed city is Fairview Heights, 4.3 mi away.
Topography around O'Fallon
How much the land rises and falls, and what covers it, within 2, 10 and 50 miles of O'Fallon.
Within 2 miles, the terrain around O'Fallon has only modest variations in elevation — a maximum elevation change of 177 ft around an average of 548 ft above sea level; within 10 miles, only modest variations in elevation — a maximum elevation change of 295 ft; within 50 miles, significant variations in elevation — a maximum elevation change of 958 ft.
The land around O'Fallon is covered by trees (37%), artificial surfaces (23%) and grassland (21%) within 2 miles, cropland (41%) and trees (36%) within 10 miles, and cropland (48%) and trees (39%) within 50 miles.
United States travel facts
- Power plugs
- Type A / B
- 120 V · 60 Hz
- Prices
- ≈ 100% of US
- price level, 2025
- GDP per capita
- $90,027
- 2025
- Happiness
- 6.8 / 10
- World Happiness, 2025
- Safe drinking water
- 98%
- of population, 2024
- Homicide rate
- 5.8
- per 100k, 2023
- Road deaths
- 12.7
- per 100k/yr, 2019
- Income group
- High
- World Bank
- Religion
Sources: World Bank, US State Department, World Happiness Report, WHO/UNICEF, EF EPI, CIA World Factbook.
Data sources
Temperature, precipitation, cloud, humidity, wind and solar figures are a 1991–2020 climatology for O'Fallon (38.5923°, -89.9112°, elevation 548 ft), computed from hourly ERA5 reanalysis — contains modified Copernicus Climate Change Service information. Sun figures are astronomical calculations, not observations. City data © GeoNames, CC BY 4.0. Map outlines from Natural Earth (public domain); interactive map © Google.