S
M
T
W
T
F
S
26
97°
77°
27
91°
78°
28
89°
73°
29
87°
68°
30
84°
66°
31
79°
63°
1
82°
62°
2
83°
63°
3
85°
64°
4
83°
65°
5
78°
64°
6
81°
63°
7
84°
65°
8
85°
66°
9
86°
65°
10
86°
65°
11
88°
64°
12
85°
63°
13
87°
62°
14
84°
63°
15
81°
66°
16
87°
67°
17
90°
69°
18
89°
69°
19
90°
68°
20
88°
67°
21
88°
68°
22
90°
67°
23
88°
66°
24
87°
67°
25
88°
65°
26
86°
64°
27
86°
64°
28
87°
63°
29
86°
64°
30
87°
65°
31
87°
64°
1
88°
65°
2
88°
65°
3
87°
64°
4
87°
64°
5
86°
63°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
August Weather in St. Charles
St. Charles's August 2026 forecast shows daily high temperatures ranging from 78° to 90°, with overnight lows between 62° and 69°. The average high for August is 86° with an average low of 65°. 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 St. Charles. See also: September | October | November.
