O'Fallon · first 14 days — live forecast · rest of month — climate corridor
🗺️ 14-day forecast map
O'Fallon & neighbors — hit play
Every city on the map carries real forecast data from the same models as its city page, refreshed several times a day. The icon is the day's overall look; the number is the afternoon high.
Next 14 days at a glance
from the model forecast
Hottest day
42°
Wed, Sep 9
Coldest night
18°
Fri, Aug 28
Days with precip
1 / 14
of 14 forecast days
Nicest day
Fri, Aug 28
mild, dry, light wind
The next 4 weekends
plan ahead
Sat 29 – Sun 30 Aug
35° 18°
10% precip chance
Sat 5 – Sun 6 Sep
41° 28°
57% precip chance
Sat 12 – Sun 13 Sep
36° 22°
typical range
Sat 19 – Sun 20 Sep
35° 22°
typical range
30 days — O'Fallon
14 forecast + 16 climatology
Thu · Today Sunny
32°19°4%⌄
Wind9 mph N
Gusts15 mph
UV index8 – High
Precip chance4%
Sunrise06:24
Sunset19:37
Fri · Tomorrow Sunny
28°18°5%⌄
Wind7 mph NE
Gusts15 mph
UV index7 – High
Precip chance5%
Sunrise06:25
Sunset19:36
Saturday 29/8 Mostly cloudy
30°18°10%⌄
Wind9 mph SE
Gusts21 mph
UV index7 – High
Precip chance10%
Sunrise06:26
Sunset19:34
Sunday 30/8 Mostly cloudy
35°21°6%⌄
Wind13 mph S
Gusts33 mph
UV index8 – Very high
Precip chance6%
Sunrise06:27
Sunset19:33
Monday 31/8 Sunny
36°25°3%⌄
Wind17 mph S
Gusts38 mph
UV index9 – Very high
Precip chance3%
Sunrise06:28
Sunset19:31
Tuesday 1/9 Sunny
40°27°1%⌄
Wind15 mph S
Gusts37 mph
UV index9 – Very high
Precip chance1%
Sunrise06:29
Sunset19:30
Wednesday 2/9 Sunny
39°27°1%⌄
Wind10 mph W
Gusts27 mph
UV index9 – Very high
Precip chance1%
Sunrise06:29
Sunset19:28
Thursday 3/9 Sunny
40°28°1%⌄
Wind9 mph SW
Gusts19 mph
UV index10 – Very high
Precip chance1%
Sunrise06:30
Sunset19:27
Friday 4/9 Sunny
40°27°1%⌄
Wind14 mph SW
Gusts18 mph
UV index10 – Very high
Precip chance1%
Sunrise06:31
Sunset19:25
Saturday 5/9 Sunny
41°28°1%⌄
Wind13 mph SW
Gusts20 mph
UV index10 – Very high
Precip chance1%
Sunrise06:32
Sunset19:24
Sunday 6/9 Showers
38°28°2.7 mm⌄
Wind9 mph W
Gusts17 mph
UV index9 – Very high
Precip chance57%
Sunrise06:33
Sunset19:22
Monday 7/9 Sunny
38°26°0.3 mm⌄
Wind7 mph SW
Gusts12 mph
UV index9 – Very high
Precip chance36%
Sunrise06:34
Sunset19:21
Tuesday 8/9 Sunny
40°26°1%⌄
Wind13 mph SW
Gusts24 mph
UV index9 – Very high
Precip chance1%
Sunrise06:35
Sunset19:19
Wednesday 9/9 Sunny
42°28°1%⌄
Wind18 mph W
Gusts33 mph
UV index10 – Very high
Precip chance1%
Sunrise06:36
Sunset19:17
Thursday 10/9 Light rain (climatological)
32°21°1.1 mm⌄
Day≈29–35°
Night≈18–24°
Precip≈0.6 in / September
(climatological)Typical range for these dates · 1991–2020
Friday 11/9 Partly cloudy (climatological)
36°23°20%⌄
Day≈33–39°
Night≈20–26°
Precip≈0.6 in / September
(climatological)Typical range for these dates · 1991–2020
Saturday 12/9 Partly cloudy (climatological)
36°23°20%⌄
Day≈33–39°
Night≈20–26°
Precip≈0.6 in / September
(climatological)Typical range for these dates · 1991–2020
Sunday 13/9 Light rain (climatological)
35°22°1.3 mm⌄
Day≈32–38°
Night≈19–25°
Precip≈0.6 in / September
(climatological)Typical range for these dates · 1991–2020
Monday 14/9 Partly cloudy (climatological)
32°20°20%⌄
Day≈29–35°
Night≈17–23°
Precip≈0.6 in / September
(climatological)Typical range for these dates · 1991–2020
Tuesday 15/9 Partly cloudy (climatological)
31°20°20%⌄
Day≈28–34°
Night≈17–23°
Precip≈0.6 in / September
(climatological)Typical range for these dates · 1991–2020
Wednesday 16/9 Light rain (climatological)
32°20°0.8 mm⌄
Day≈29–35°
Night≈17–23°
Precip≈0.6 in / September
(climatological)Typical range for these dates · 1991–2020
Thursday 17/9 Partly cloudy (climatological)
33°21°20%⌄
Day≈30–36°
Night≈18–24°
Precip≈0.6 in / September
(climatological)Typical range for these dates · 1991–2020
Friday 18/9 Partly cloudy (climatological)
34°22°20%⌄
Day≈31–37°
Night≈19–25°
Precip≈0.6 in / September
(climatological)Typical range for these dates · 1991–2020
Saturday 19/9 Light rain (climatological)
35°22°2.0 mm⌄
Day≈32–38°
Night≈19–25°
Precip≈0.6 in / September
(climatological)Typical range for these dates · 1991–2020
Sunday 20/9 Partly cloudy (climatological)
34°22°20%⌄
Day≈31–37°
Night≈19–25°
Precip≈0.6 in / September
(climatological)Typical range for these dates · 1991–2020
Monday 21/9 Partly cloudy (climatological)
32°20°20%⌄
Day≈29–35°
Night≈17–23°
Precip≈0.6 in / September
(climatological)Typical range for these dates · 1991–2020
Tuesday 22/9 Light rain (climatological)
32°20°2.0 mm⌄
Day≈29–35°
Night≈17–23°
Precip≈0.6 in / September
(climatological)Typical range for these dates · 1991–2020
Wednesday 23/9 Partly cloudy (climatological)
31°20°20%⌄
Day≈28–34°
Night≈17–23°
Precip≈0.6 in / September
(climatological)Typical range for these dates · 1991–2020
Thursday 24/9 Partly cloudy (climatological)
33°21°20%⌄
Day≈30–36°
Night≈18–24°
Precip≈0.6 in / September
(climatological)Typical range for these dates · 1991–2020
Friday 25/9 Light rain (climatological)
37°23°1.6 mm⌄
Day≈34–40°
Night≈20–26°
Precip≈0.6 in / September
(climatological)Typical range for these dates · 1991–2020
How does a 30-day outlook work?
The first 14 days are a live model forecast. The back half of the month shows the typical range for those dates — useful for planning, not a literal prediction.
First 14 days: a real forecast, blended from NBM, ECMWF and GFS runs. Trust it most inside three days; by the second week treat it as a lean, not a promise.
Rest of the month: past day 14 we stop pretending to forecast and switch to the climate corridor — the range those dates have produced over three decades computed directly for O'Fallon, with mild week-to-week wiggle.
Good question for this page: "Is late August usually humid in Chicago?" Bad question: "Do I need an umbrella on the 29th?" — three weeks out no one knows, and that's the honest answer.