O'Fallon weather in April

In April, O'Fallon sees average daytime highs of 66°F and overnight lows near 47°F, with 4.5 in of precipitation across 11.3 wet days and about 13 hours of daylight. It is the 7th-warmest and 2nd-wettest month of the year here.

Highs climb over the month, from about 62°F in the first days to 69°F by the end. The sky is clear or mostly clear about 30% of the time in April, and the air most often feels dry.

Daylight stretches from about 12 h 24 min at the start of April to 13 h 36 min by month's end. Set against the rest of the year, April is O'Fallon's 7th-clearest and 1st-windiest month. For the whole year in context, see O'Fallon's year-round climate.

Daytime high
66°
7th warmest
Overnight low
47°
6th coldest
Precipitation
4.5 in
11.3 wet days
Daylight
13 hours
5:33 AM – 6:33 PM
Cloud cover
60%
7th clearest
Wind
8 mph
1st windiest
Solar energy
5.15 kWh/m²
Travel score
5.8
out of 10

O'Fallon is city in St. Charles County, Missouri, United States.

Density
1,105/km²
people per km²
Founded
1856

Air quality: WHO Ambient Air Quality Database. Density & description: Wikidata (CC0), GeoNames.

Temperature in April

Average highAverage lowShaded bands: 10–90% of days

Highs climb over the month, from about 62°F in the first days to 69°F by the end.

A typical April day in O'Fallon reaches about 66°F in the afternoon and slips back to 47°F overnight — a 19°F spread between the day's warmth and the night's chill. On most days the high lands between 52°F and 80°F. Set against its neighbours, April runs about 11°F warmer than March and about 9°F cooler than May.

20°40°60°80°151015202530
Avg high (°F)Avg low (°F)
16142
26242
36243
46343
56344
66444
76444
86444
96545
106545
116546
126646
136646
146647
156647
166747
176747
186748
196748
206748
216849
226849
236849
246850
256950
266950
276951
286951
297051
307052

How April really feels in O'Fallon

Once humidity and wind are folded in, April averages 0 days that feel above 90°F and 0 that feel at or below 32°F — the comfort signal a plain temperature reading hides.

Days feeling ≥ 90°F
0
heat index over the day's high
Days feeling ≤ 32°F
0
wind chill below the day's low

April sits comfortably in between — no days that feel dangerously hot or drop to a hard freeze once humidity and wind are folded in.

O'Fallon weather by month

How April compares with the rest of the year at a glance. April is the 7th-warmest and 2nd-wettest month here — the current month is highlighted below.

MonthHigh / Low (°F)Rainfall (inches)Wet daysSnow daysDaylight (hours)Travel score
Jan40° / 24°2.57.739.60.0
Feb44° / 28°2.47.62.910.50.8
Mar55° / 37°3.610.61.411.73.5
Apr66° / 47°4.511.30.2135.8
May75° / 57°4.913.3014.16.3
Jun84° / 66°4.011.1014.75.5
Jul87° / 70°3.29.9014.44.6
Aug86° / 67°3.09.2013.55.2
Sep79° / 59°3.27.6012.37.1
Oct67° / 48°3.38.50116.6
Nov54° / 37°3.58.30.89.93.5
Dec43° / 28°2.47.72.29.30.6

Cloud cover in April

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 30% of the time in April.

Beyond those clear spells, partly cloudy skies cover about 15% of April, with mostly cloudy or overcast conditions the remaining 55%.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
14357
24357
34456
44456
54654
64753
74753
84753
94852
104753
114951
124852
134951
144753
154753
164654
174753
184654
194654
204555
214456
224357
234357
244357
254357
264357
274258
284258
294258
304258

Chance of precipitation in April

Any precipitationSnow

O'Fallon gets around 4.5 in of rain and snow over 11.3 wet days in April. The line is the day-by-day chance of measurable precipitation.

Day to day, the chance of measurable precipitation averages around 38% and peaks near 45% on the wettest days, and about 0 day brings snow. The odds climb toward the end of the month.

0%20%40%60%151015202530
Rain chance (%)Snow chance (%)
1352
2352
3352
4342
5342
6341
7341
8341
9341
10341
11341
12341
13351
14351
15361
16371
17380
18380
19390
20400
21410
22420
23430
24440
25440
26450
27450
28450
29450
30450

Humidity in April

DryComfortableHumidMuggyOppressiveMiserable

Most of April feels dry — the stacked bands show each day's mix of comfort levels, read off the dew point.

By dew point, April lands in the dry band about 84% of days. It rarely turns muggy — the humid and sticky bands barely register.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)Muggy (%)
191630
290730
390730
490730
590730
688840
788840
888840
987940
1087940
11861040
12861040
13851140
14851140
15841240
16841240
17841240
18831340
19831340
20831340
21811450
22811450
23811450
24801550
25791560
26781561
27761671
28751771
29741781
30711892

Wind in April

Winds average 8 mph in April, the windiest month of the year.

Across April, daily wind ranges from about 7 mph on the calmest days to 8 mph at its breeziest. It stays fairly steady from day to day.

0246810151015202530
Wind speed (mph)Feels
18light breeze
28light breeze
38light breeze
48light breeze
58light breeze
68light breeze
78light breeze
88light breeze
98light breeze
108light breeze
118light breeze
128light breeze
138light breeze
148light breeze
158light breeze
168light breeze
178light breeze
188light breeze
198light breeze
208light breeze
218light breeze
228light breeze
238light breeze
248light breeze
258light breeze
268light breeze
277light breeze
287calm
297calm
307calm

Sunrise & sunset in April

DaylightNight

Daylight runs from about 12 h 24 min at the start of April to 13 h 36 min by month's end. The lit band spans sunrise to sunset each day.

Days grow by about 72 minutes over April. Sunrise moves from 5:56 AM to 5:13 AM, and sunset from 6:19 PM to 6:47 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
112.45:566:19
212.45:556:20
312.55:536:21
412.55:516:22
512.55:506:23
612.65:486:24
712.65:476:25
812.75:456:26
912.75:436:27
1012.85:426:28
1112.85:406:28
1212.85:396:29
1312.95:376:30
1412.95:366:31
1513.05:346:32
1613.05:336:33
1713.15:316:34
1813.15:306:35
1913.15:286:36
2013.25:276:37
2113.25:256:38
2213.35:246:39
2313.35:236:40
2413.35:216:41
2513.45:206:42
2613.45:186:43
2713.45:176:44
2813.55:166:45
2913.55:156:46
3013.65:136:47

Solar energy in April

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in April, about 5.15 kWh/m².

For context, solar energy here swings from a low near 1.92 kWh/m² to a high of 6.42 kWh/m² in June across the year — April's 5.15 kWh/m² falls in the middle.

0246151015202530
Solar energy (kWh/m²)Level
14.7Bright
24.8Bright
34.8Bright
44.9Bright
54.9Bright
65.0Bright
75.0Bright
85.0Bright
95.1Bright
105.1Bright
115.1Bright
125.1Bright
135.1Bright
145.2Bright
155.2Bright
165.2Bright
175.2Bright
185.2Bright
195.2Bright
205.2Bright
215.2Bright
225.2Bright
235.2Bright
245.2Bright
255.2Bright
265.2Bright
275.2Bright
285.3Bright
295.3Bright
305.3Bright
Planning a trip in April

Is April a good time to visit O'Fallon?

Our two travel scores rate April for general sightseeing and for beach or pool weather — 0 (poor) to 10 (ideal).

5.8
Sightseeing
4th-best month of the year
2.5
Beach & pool
7th-best month of the year

April is a reasonable time to visit O'Fallon for sightseeing.

What to pack for O'Fallon in April

From April's temperature range, rain chance, sun and wind — what's worth putting in the bag.

In April, O'Fallon sees daytime highs around 66°F and nights near 47°F. Worth packing: rain gear and sun protection. About 11 days see rain.

rain gearsun protection

UV index in O'Fallon in April

LowModerateHighVery highExtreme

Clear-sky midday UV in April peaks 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 January 1 at about 2 (low).

The index reaches 3 or more — the level where the WHO recommends sun protection — in 10 months of the year.

025710JanFebMarAprMayJunJulAugSepOctNovDecModerateHighVery highHighModerateJun 22UV 9Jan 1UV 2
UV index (midday)Level
Jan2Low
Feb3Moderate
Mar5Moderate
Apr7High
May8Very high
Jun9Very high
Jul9Very high
Aug8Very high
Sep7High
Oct4Moderate
Nov3Moderate
Dec2Low

Air quality in O'Fallon in April

GoodModeratePoorUnhealthyVery unhealthy

Average fine-particle pollution (PM2.5) through the year — so you can see where April falls, not just the annual average.

Air quality in O'Fallon is worst in July — around 17 µg/m³ PM2.5 (moderate), about 2.3× the cleanest month (October, 7 µg/m³).

Modeled monthly averages (CAMS reanalysis, 2015–2024).

01020JanFebMarAprMayJunJulAugSepOctNovDecGoodModerateGoodJul 1616 µg/m³Oct 237 µg/m³
PM2.5 (µg/m³)Level
Jan9Good
Feb11Good
Mar11Good
Apr10Good
May13Moderate
Jun14Moderate
Jul17Moderate
Aug14Moderate
Sep11Good
Oct7Good
Nov7Good
Dec8Good
Location & terrain

Where is O'Fallon?

O'Fallon sits at 38.8°N, 90.7°W, 541 ft above sea level, in United States. The nearest listed city is Saint Peters, 3.7 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 207 ft around an average of 535 ft above sea level; within 10 miles, only modest variations in elevation — a maximum elevation change of 413 ft; within 50 miles, significant variations in elevation — a maximum elevation change of 928 ft.

The land around O'Fallon is covered by trees (43%), artificial surfaces (34%) and grassland (20%) within 2 miles, trees (41%) and cropland (24%) within 10 miles, and trees (52%) and cropland (31%) within 50 miles.

2 miles
207 ft
10 miles
413 ft
50 miles
928 ft
treesgrasslandcroplandartificial surfacesbare terrainwater
April weather nearby: Saint Peters 3.7 mi · Wentzville 8.1 mi · Saint Charles 12 mi · Chesterfield 12 mi · Wildwood 16 mi · Maryland Heights 16 mi · Ballwin 17 mi · Hazelwood 18 mi

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
Protestant 47%unaffiliated 23%Roman Catholic 21%Jewish 2%

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 (38.8106°, -90.6998°, elevation 541 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. UV index is derived from CAMS (Copernicus Atmosphere Monitoring Service) clear-sky UV data — contains modified Copernicus Atmosphere Monitoring Service information. Monthly air-quality (PM2.5) seasonality is from the CAMS EAC4 reanalysis (Copernicus Atmosphere Monitoring Service), scaled to the WHO annual mean where available. Topography is sampled from the Copernicus DEM GLO-90 elevation model (© ESA/Airbus) and ESA WorldCover 2021 land cover (CC BY 4.0).