O'Fallon weather in July
In July, O'Fallon sees average daytime highs of 87°F and overnight lows near 70°F, with 3.2 in of rain across 9.9 wet days and about 14.4 hours of daylight. It is the 1st-warmest and 7th-wettest month of the year here.
Day-to-day highs hold fairly steady near 87°F through the month. The sky is clear or mostly clear about 39% of the time in July, and the air most often feels oppressive.
Daylight stretches from about 14 h 42 min at the start of July to 14 h 06 min by month's end. Set against the rest of the year, July is O'Fallon's 4th-clearest and 11th-windiest month. For the whole year in context, see O'Fallon's year-round climate.
- Daytime high
- 87°
- 1st warmest
- Overnight low
- 70°
- 12th coldest
- Rainfall
- 3.2 in
- 9.9 wet days
- Daylight
- 14 h 30 min
- 4:54 AM – 7:22 PM
- Cloud cover
- 52%
- 4th clearest
- Wind
- 5 mph
- 11th windiest
- Solar energy
- 6.4 kWh/m²
- Travel score
- 4.6
- 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 July
Day-to-day highs hold fairly steady near 87°F through the month.
A typical July day in O'Fallon reaches about 87°F in the afternoon and slips back to 70°F overnight — a 17°F spread between the day's warmth and the night's chill. On most days the high lands between 80°F and 95°F. Set against its neighbours, July runs about 4°F warmer than June and about 1°F warmer than August.
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg high (°F) | 87 | 87 | 87 | 87 | 87 | 87 | 87 | 87 | 87 | 88 | 88 | 88 | 88 | 88 | 88 | 88 | 88 | 88 | 88 | 88 | 88 | 88 | 88 | 88 | 88 | 87 | 87 | 87 | 87 | 87 | 87 |
| Avg low (°F) | 69 | 69 | 69 | 69 | 70 | 70 | 70 | 70 | 70 | 70 | 70 | 70 | 70 | 71 | 71 | 71 | 71 | 71 | 71 | 70 | 70 | 70 | 70 | 70 | 70 | 70 | 70 | 70 | 69 | 69 | 69 |
| Avg high (°F) | Avg low (°F) | |
|---|---|---|
| 1 | 87 | 69 |
| 2 | 87 | 69 |
| 3 | 87 | 69 |
| 4 | 87 | 69 |
| 5 | 87 | 70 |
| 6 | 87 | 70 |
| 7 | 87 | 70 |
| 8 | 87 | 70 |
| 9 | 87 | 70 |
| 10 | 88 | 70 |
| 11 | 88 | 70 |
| 12 | 88 | 70 |
| 13 | 88 | 70 |
| 14 | 88 | 71 |
| 15 | 88 | 71 |
| 16 | 88 | 71 |
| 17 | 88 | 71 |
| 18 | 88 | 71 |
| 19 | 88 | 71 |
| 20 | 88 | 70 |
| 21 | 88 | 70 |
| 22 | 88 | 70 |
| 23 | 88 | 70 |
| 24 | 88 | 70 |
| 25 | 88 | 70 |
| 26 | 87 | 70 |
| 27 | 87 | 70 |
| 28 | 87 | 70 |
| 29 | 87 | 69 |
| 30 | 87 | 69 |
| 31 | 87 | 69 |
How July really feels in O'Fallon
Once humidity and wind are folded in, July averages 27 days that feel above 90°F and 0 that feel at or below 32°F — the comfort signal a plain temperature reading hides.
The story in July is heat — humidity pushes the afternoon "feels like" well above the raw temperature.
O'Fallon weather by month
How July compares with the rest of the year at a glance. July is the 1st-warmest and 7th-wettest month here — the current month is highlighted below.
| Month | High / Low (°F) | Rainfall (inches) | Wet days | Snow days | Daylight (hours) | Travel score |
|---|---|---|---|---|---|---|
| Jan | 40° / 24° | 2.5 | 7.7 | 3 | 9.6 | 0.0 |
| Feb | 44° / 28° | 2.4 | 7.6 | 2.9 | 10.5 | 0.8 |
| Mar | 55° / 37° | 3.6 | 10.6 | 1.4 | 11.7 | 3.5 |
| Apr | 66° / 47° | 4.5 | 11.3 | 0.2 | 13 | 5.8 |
| May | 75° / 57° | 4.9 | 13.3 | 0 | 14.1 | 6.3 |
| Jun | 84° / 66° | 4.0 | 11.1 | 0 | 14.7 | 5.5 |
| Jul | 87° / 70° | 3.2 | 9.9 | 0 | 14.4 | 4.6 |
| Aug | 86° / 67° | 3.0 | 9.2 | 0 | 13.5 | 5.2 |
| Sep | 79° / 59° | 3.2 | 7.6 | 0 | 12.3 | 7.1 |
| Oct | 67° / 48° | 3.3 | 8.5 | 0 | 11 | 6.6 |
| Nov | 54° / 37° | 3.5 | 8.3 | 0.8 | 9.9 | 3.5 |
| Dec | 43° / 28° | 2.4 | 7.7 | 2.2 | 9.3 | 0.6 |
Cloud cover in July
The sky is clear or mostly clear about 39% of the time in July.
Beyond those clear spells, partly cloudy skies cover about 19% of July, with mostly cloudy or overcast conditions the remaining 42%.
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Clearer (%) | 57 | 58 | 58 | 58 | 58 | 58 | 58 | 59 | 59 | 59 | 59 | 58 | 58 | 58 | 58 | 58 | 58 | 58 | 57 | 57 | 57 | 57 | 57 | 57 | 57 | 58 | 57 | 57 | 58 | 58 | 58 |
| Cloudier (%) | 43 | 42 | 42 | 42 | 42 | 42 | 42 | 41 | 41 | 41 | 41 | 42 | 42 | 42 | 42 | 42 | 42 | 42 | 43 | 43 | 43 | 43 | 43 | 43 | 43 | 42 | 43 | 43 | 42 | 42 | 42 |
| Clearer (%) | Cloudier (%) | |
|---|---|---|
| 1 | 57 | 43 |
| 2 | 58 | 42 |
| 3 | 58 | 42 |
| 4 | 58 | 42 |
| 5 | 58 | 42 |
| 6 | 58 | 42 |
| 7 | 58 | 42 |
| 8 | 59 | 41 |
| 9 | 59 | 41 |
| 10 | 59 | 41 |
| 11 | 59 | 41 |
| 12 | 58 | 42 |
| 13 | 58 | 42 |
| 14 | 58 | 42 |
| 15 | 58 | 42 |
| 16 | 58 | 42 |
| 17 | 58 | 42 |
| 18 | 58 | 42 |
| 19 | 57 | 43 |
| 20 | 57 | 43 |
| 21 | 57 | 43 |
| 22 | 57 | 43 |
| 23 | 57 | 43 |
| 24 | 57 | 43 |
| 25 | 57 | 43 |
| 26 | 58 | 42 |
| 27 | 57 | 43 |
| 28 | 57 | 43 |
| 29 | 58 | 42 |
| 30 | 58 | 42 |
| 31 | 58 | 42 |
Chance of precipitation in July
O'Fallon gets around 3.2 in of rain over 9.9 wet days in July. The line is the day-by-day chance of measurable precipitation.
Day to day, the chance of measurable rain averages around 32% and peaks near 36% on the wettest days.
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Rain chance (%) | 36 | 36 | 36 | 35 | 35 | 34 | 34 | 33 | 32 | 32 | 31 | 30 | 30 | 30 | 30 | 30 | 30 | 30 | 30 | 30 | 30 | 30 | 31 | 31 | 31 | 32 | 32 | 32 | 32 | 32 | 32 |
| Rain chance (%) | |
|---|---|
| 1 | 36 |
| 2 | 36 |
| 3 | 36 |
| 4 | 35 |
| 5 | 35 |
| 6 | 34 |
| 7 | 34 |
| 8 | 33 |
| 9 | 32 |
| 10 | 32 |
| 11 | 31 |
| 12 | 30 |
| 13 | 30 |
| 14 | 30 |
| 15 | 30 |
| 16 | 30 |
| 17 | 30 |
| 18 | 30 |
| 19 | 30 |
| 20 | 30 |
| 21 | 30 |
| 22 | 30 |
| 23 | 31 |
| 24 | 31 |
| 25 | 31 |
| 26 | 32 |
| 27 | 32 |
| 28 | 32 |
| 29 | 32 |
| 30 | 32 |
| 31 | 32 |
Humidity in July
Most of July feels oppressive — the stacked bands show each day's mix of comfort levels, read off the dew point.
By dew point, July lands in the oppressive band about 37% of days. Sticky, muggy-or-worse air turns up on roughly 68% of them.
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Dry (%) | 4 | 4 | 3 | 3 | 3 | 3 | 3 | 2 | 2 | 2 | 2 | 2 | 2 | 2 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 2 | 2 | 2 | 2 | 2 |
| Comfortable (%) | 13 | 13 | 13 | 12 | 12 | 12 | 11 | 11 | 10 | 9 | 9 | 9 | 8 | 8 | 8 | 9 | 9 | 9 | 10 | 10 | 11 | 11 | 12 | 12 | 12 | 13 | 13 | 13 | 13 | 13 | 13 |
| Humid (%) | 21 | 21 | 20 | 20 | 20 | 20 | 20 | 19 | 19 | 19 | 19 | 18 | 18 | 18 | 18 | 18 | 18 | 19 | 19 | 19 | 19 | 19 | 19 | 20 | 20 | 21 | 21 | 21 | 21 | 21 | 21 |
| Muggy (%) | 31 | 30 | 30 | 29 | 29 | 29 | 29 | 30 | 30 | 31 | 31 | 31 | 31 | 31 | 30 | 30 | 29 | 28 | 27 | 27 | 26 | 26 | 25 | 25 | 25 | 25 | 25 | 26 | 26 | 27 | 28 |
| Oppressive (%) | 31 | 32 | 33 | 34 | 34 | 35 | 35 | 36 | 36 | 37 | 37 | 38 | 38 | 39 | 39 | 39 | 39 | 40 | 40 | 40 | 40 | 40 | 40 | 40 | 39 | 38 | 37 | 36 | 35 | 34 | 34 |
| Miserable (%) | 1 | 1 | 1 | 1 | 1 | 2 | 2 | 2 | 2 | 2 | 2 | 2 | 3 | 3 | 3 | 3 | 3 | 3 | 3 | 3 | 3 | 3 | 3 | 3 | 3 | 2 | 2 | 2 | 2 | 2 | 2 |
| Dry (%) | Comfortable (%) | Humid (%) | Muggy (%) | Oppressive (%) | Miserable (%) | |
|---|---|---|---|---|---|---|
| 1 | 4 | 13 | 21 | 31 | 31 | 1 |
| 2 | 4 | 13 | 21 | 30 | 32 | 1 |
| 3 | 3 | 13 | 20 | 30 | 33 | 1 |
| 4 | 3 | 12 | 20 | 29 | 34 | 1 |
| 5 | 3 | 12 | 20 | 29 | 34 | 1 |
| 6 | 3 | 12 | 20 | 29 | 35 | 2 |
| 7 | 3 | 11 | 20 | 29 | 35 | 2 |
| 8 | 2 | 11 | 19 | 30 | 36 | 2 |
| 9 | 2 | 10 | 19 | 30 | 36 | 2 |
| 10 | 2 | 9 | 19 | 31 | 37 | 2 |
| 11 | 2 | 9 | 19 | 31 | 37 | 2 |
| 12 | 2 | 9 | 18 | 31 | 38 | 2 |
| 13 | 2 | 8 | 18 | 31 | 38 | 3 |
| 14 | 2 | 8 | 18 | 31 | 39 | 3 |
| 15 | 1 | 8 | 18 | 30 | 39 | 3 |
| 16 | 1 | 9 | 18 | 30 | 39 | 3 |
| 17 | 1 | 9 | 18 | 29 | 39 | 3 |
| 18 | 1 | 9 | 19 | 28 | 40 | 3 |
| 19 | 1 | 10 | 19 | 27 | 40 | 3 |
| 20 | 1 | 10 | 19 | 27 | 40 | 3 |
| 21 | 1 | 11 | 19 | 26 | 40 | 3 |
| 22 | 1 | 11 | 19 | 26 | 40 | 3 |
| 23 | 1 | 12 | 19 | 25 | 40 | 3 |
| 24 | 1 | 12 | 20 | 25 | 40 | 3 |
| 25 | 1 | 12 | 20 | 25 | 39 | 3 |
| 26 | 1 | 13 | 21 | 25 | 38 | 2 |
| 27 | 2 | 13 | 21 | 25 | 37 | 2 |
| 28 | 2 | 13 | 21 | 26 | 36 | 2 |
| 29 | 2 | 13 | 21 | 26 | 35 | 2 |
| 30 | 2 | 13 | 21 | 27 | 34 | 2 |
| 31 | 2 | 13 | 21 | 28 | 34 | 2 |
Wind in July
Winds average 5 mph in July.
Across July, daily wind ranges from about 5 mph on the calmest days to 5 mph at its breeziest. It stays fairly steady from day to day.
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Wind speed (mph) | 5 | 5 | 5 | 5 | 5 | 5 | 5 | 5 | 5 | 5 | 5 | 5 | 5 | 5 | 5 | 5 | 5 | 5 | 5 | 5 | 5 | 5 | 5 | 5 | 5 | 5 | 5 | 5 | 5 | 5 | 5 |
| Feels | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm |
| Wind speed (mph) | Feels | |
|---|---|---|
| 1 | 5 | calm |
| 2 | 5 | calm |
| 3 | 5 | calm |
| 4 | 5 | calm |
| 5 | 5 | calm |
| 6 | 5 | calm |
| 7 | 5 | calm |
| 8 | 5 | calm |
| 9 | 5 | calm |
| 10 | 5 | calm |
| 11 | 5 | calm |
| 12 | 5 | calm |
| 13 | 5 | calm |
| 14 | 5 | calm |
| 15 | 5 | calm |
| 16 | 5 | calm |
| 17 | 5 | calm |
| 18 | 5 | calm |
| 19 | 5 | calm |
| 20 | 5 | calm |
| 21 | 5 | calm |
| 22 | 5 | calm |
| 23 | 5 | calm |
| 24 | 5 | calm |
| 25 | 5 | calm |
| 26 | 5 | calm |
| 27 | 5 | calm |
| 28 | 5 | calm |
| 29 | 5 | calm |
| 30 | 5 | calm |
| 31 | 5 | calm |
Sunrise & sunset in July
Daylight runs from about 14 h 42 min at the start of July to 14 h 06 min by month's end. The lit band spans sunrise to sunset each day.
Days shrink by about 36 minutes over July. Sunrise moves from 4:46 AM to 5:07 AM, and sunset from 7:27 PM to 7:11 PM.
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Daylight (h) | 14.7 | 14.7 | 14.7 | 14.7 | 14.6 | 14.6 | 14.6 | 14.6 | 14.6 | 14.6 | 14.6 | 14.5 | 14.5 | 14.5 | 14.5 | 14.5 | 14.4 | 14.4 | 14.4 | 14.4 | 14.4 | 14.3 | 14.3 | 14.3 | 14.3 | 14.2 | 14.2 | 14.2 | 14.1 | 14.1 | 14.1 |
| Sunrise (AM) | 4:46 | 4:46 | 4:46 | 4:47 | 4:47 | 4:48 | 4:49 | 4:49 | 4:50 | 4:50 | 4:51 | 4:52 | 4:52 | 4:53 | 4:54 | 4:54 | 4:55 | 4:56 | 4:57 | 4:57 | 4:58 | 4:59 | 5:00 | 5:01 | 5:01 | 5:02 | 5:03 | 5:04 | 5:05 | 5:06 | 5:07 |
| Sunset (PM) | 7:27 | 7:27 | 7:27 | 7:26 | 7:26 | 7:26 | 7:26 | 7:26 | 7:25 | 7:25 | 7:25 | 7:24 | 7:24 | 7:23 | 7:23 | 7:22 | 7:22 | 7:21 | 7:21 | 7:20 | 7:19 | 7:19 | 7:18 | 7:17 | 7:17 | 7:16 | 7:15 | 7:14 | 7:13 | 7:12 | 7:11 |
| Daylight (h) | Sunrise (AM) | Sunset (PM) | |
|---|---|---|---|
| 1 | 14.7 | 4:46 | 7:27 |
| 2 | 14.7 | 4:46 | 7:27 |
| 3 | 14.7 | 4:46 | 7:27 |
| 4 | 14.7 | 4:47 | 7:26 |
| 5 | 14.6 | 4:47 | 7:26 |
| 6 | 14.6 | 4:48 | 7:26 |
| 7 | 14.6 | 4:49 | 7:26 |
| 8 | 14.6 | 4:49 | 7:26 |
| 9 | 14.6 | 4:50 | 7:25 |
| 10 | 14.6 | 4:50 | 7:25 |
| 11 | 14.6 | 4:51 | 7:25 |
| 12 | 14.5 | 4:52 | 7:24 |
| 13 | 14.5 | 4:52 | 7:24 |
| 14 | 14.5 | 4:53 | 7:23 |
| 15 | 14.5 | 4:54 | 7:23 |
| 16 | 14.5 | 4:54 | 7:22 |
| 17 | 14.4 | 4:55 | 7:22 |
| 18 | 14.4 | 4:56 | 7:21 |
| 19 | 14.4 | 4:57 | 7:21 |
| 20 | 14.4 | 4:57 | 7:20 |
| 21 | 14.4 | 4:58 | 7:19 |
| 22 | 14.3 | 4:59 | 7:19 |
| 23 | 14.3 | 5:00 | 7:18 |
| 24 | 14.3 | 5:01 | 7:17 |
| 25 | 14.3 | 5:01 | 7:17 |
| 26 | 14.2 | 5:02 | 7:16 |
| 27 | 14.2 | 5:03 | 7:15 |
| 28 | 14.2 | 5:04 | 7:14 |
| 29 | 14.1 | 5:05 | 7:13 |
| 30 | 14.1 | 5:06 | 7:12 |
| 31 | 14.1 | 5:07 | 7:11 |
Solar energy in July
Average shortwave solar energy reaching the ground each day in July, about 6.4 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 — July's 6.4 kWh/m² sits near the top of that range.
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Solar energy (kWh/m²) | 6.6 | 6.5 | 6.5 | 6.5 | 6.5 | 6.5 | 6.5 | 6.5 | 6.5 | 6.5 | 6.5 | 6.5 | 6.5 | 6.5 | 6.5 | 6.5 | 6.5 | 6.4 | 6.4 | 6.4 | 6.4 | 6.3 | 6.3 | 6.3 | 6.3 | 6.3 | 6.2 | 6.2 | 6.2 | 6.2 | 6.2 |
| Level | Intense | Intense | Intense | Intense | Intense | Intense | Intense | Intense | Intense | Intense | Intense | Intense | Intense | Intense | Intense | Intense | Intense | Intense | Intense | Intense | Intense | Intense | Intense | Intense | Intense | Intense | Intense | Intense | Intense | Intense | Intense |
| Solar energy (kWh/m²) | Level | |
|---|---|---|
| 1 | 6.6 | Intense |
| 2 | 6.5 | Intense |
| 3 | 6.5 | Intense |
| 4 | 6.5 | Intense |
| 5 | 6.5 | Intense |
| 6 | 6.5 | Intense |
| 7 | 6.5 | Intense |
| 8 | 6.5 | Intense |
| 9 | 6.5 | Intense |
| 10 | 6.5 | Intense |
| 11 | 6.5 | Intense |
| 12 | 6.5 | Intense |
| 13 | 6.5 | Intense |
| 14 | 6.5 | Intense |
| 15 | 6.5 | Intense |
| 16 | 6.5 | Intense |
| 17 | 6.5 | Intense |
| 18 | 6.4 | Intense |
| 19 | 6.4 | Intense |
| 20 | 6.4 | Intense |
| 21 | 6.4 | Intense |
| 22 | 6.3 | Intense |
| 23 | 6.3 | Intense |
| 24 | 6.3 | Intense |
| 25 | 6.3 | Intense |
| 26 | 6.3 | Intense |
| 27 | 6.2 | Intense |
| 28 | 6.2 | Intense |
| 29 | 6.2 | Intense |
| 30 | 6.2 | Intense |
| 31 | 6.2 | Intense |
Is July a good time to visit O'Fallon?
Our two travel scores rate July for general sightseeing and for beach or pool weather — 0 (poor) to 10 (ideal).
July is a reasonable time to visit O'Fallon for sightseeing. The water and warmth also suit a beach or pool day.
What to pack for O'Fallon in July
From July's temperature range, rain chance, sun and wind — what's worth putting in the bag.
In July, O'Fallon sees daytime highs around 87°F and nights near 70°F. Pack light clothes and sun protection. Worth having: rain gear. About 10 days see rain.
UV index in O'Fallon in July
Clear-sky midday UV in July peaks around 9 (very high — sun protection essential). 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.
| 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 | Low | Moderate | Moderate | High | Very high | Very high | Very high | Very high | High | Moderate | Moderate | Low |
| UV index (midday) | Level | |
|---|---|---|
| Jan | 2 | Low |
| Feb | 3 | Moderate |
| Mar | 5 | Moderate |
| 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 July
Average fine-particle pollution (PM2.5) through the year — so you can see where July 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).
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| PM2.5 (µg/m³) | 9 | 11 | 11 | 10 | 13 | 14 | 17 | 14 | 11 | 7 | 7 | 8 |
| Level | Good | Good | Good | Good | Moderate | Moderate | Moderate | Moderate | Good | Good | Good | Good |
| PM2.5 (µg/m³) | Level | |
|---|---|---|
| Jan | 9 | Good |
| Feb | 11 | Good |
| Mar | 11 | Good |
| Apr | 10 | Good |
| May | 13 | Moderate |
| Jun | 14 | Moderate |
| Jul | 17 | Moderate |
| Aug | 14 | Moderate |
| Sep | 11 | Good |
| Oct | 7 | Good |
| Nov | 7 | Good |
| Dec | 8 | Good |
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.
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 (38.8106°, -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).