S
M
T
W
T
F
S
26
98°
79°
27
97°
80°
28
90°
75°
29
85°
69°
30
87°
68°
31
81°
70°
1
78°
67°
2
83°
67°
3
86°
66°
4
89°
70°
5
89°
73°
6
79°
68°
7
91°
69°
8
91°
70°
9
94°
75°
10
98°
77°
11
97°
74°
12
93°
75°
13
94°
73°
14
93°
73°
15
96°
73°
16
91°
68°
17
86°
67°
18
85°
66°
19
89°
68°
20
90°
68°
21
90°
66°
22
89°
66°
23
86°
65°
24
82°
65°
25
84°
68°
26
88°
69°
27
87°
69°
28
88°
68°
29
84°
63°
30
78°
62°
31
79°
61°
1
79°
66°
2
80°
67°
3
82°
67°
4
87°
66°
5
83°
67°
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 98°, with overnight lows between 61° and 77°. The average high for August is 87° with an average low of 68°. 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.
