S
M
T
W
T
F
S
26
89°
70°
27
84°
71°
28
81°
62°
29
80°
58°
30
84°
57°
31
78°
65°
1
72°
66°
2
77°
63°
3
83°
59°
4
85°
62°
5
81°
66°
6
80°
67°
7
85°
64°
8
82°
64°
9
84°
61°
10
84°
68°
11
80°
67°
12
87°
67°
13
79°
64°
14
78°
65°
15
78°
66°
16
78°
64°
17
77°
62°
18
78°
63°
19
81°
65°
20
82°
65°
21
81°
63°
22
82°
62°
23
81°
61°
24
77°
64°
25
79°
65°
26
83°
65°
27
84°
64°
28
84°
64°
29
76°
61°
30
74°
61°
31
75°
60°
1
75°
62°
2
77°
63°
3
76°
64°
4
82°
63°
5
82°
64°
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 74° to 87°, with overnight lows between 60° and 68°. The average high for August is 80° with an average low of 64°. 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.
