S
M
T
W
T
F
S
26
99°
75°
27
98°
76°
28
93°
73°
29
86°
67°
30
87°
67°
31
80°
67°
1
80°
69°
2
83°
70°
3
86°
65°
4
89°
65°
5
89°
67°
6
76°
69°
7
91°
69°
8
90°
68°
9
93°
71°
10
92°
76°
11
96°
78°
12
94°
76°
13
94°
74°
14
94°
79°
15
93°
76°
16
92°
73°
17
85°
68°
18
87°
65°
19
82°
71°
20
87°
71°
21
89°
66°
22
86°
69°
23
83°
64°
24
83°
57°
25
87°
63°
26
93°
71°
27
87°
65°
28
88°
63°
29
88°
61°
30
94°
64°
31
99°
66°
1
100°
71°
2
100°
74°
3
100°
74°
4
100°
74°
5
103°
74°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
August Weather in O'Fallon
O'Fallon's August 2026 forecast shows daily high temperatures ranging from ° to °, with overnight lows between ° and °. The average high for August is ° with an average low of °. AccuWeather's monthly forecast extends further ahead than any other source, with day-by-day RealFeel® Temperatures giving a complete picture of how August weather will actually feel in O'Fallon. See also: September | October | November.
