S
M
T
W
T
F
S
30
78°
62°
31
79°
61°
1
79°
66°
2
80°
67°
3
82°
67°
4
87°
66°
5
83°
67°
6
84°
66°
7
80°
65°
8
82°
64°
9
80°
65°
10
79°
65°
11
79°
64°
12
80°
63°
13
81°
63°
14
80°
62°
15
80°
62°
16
81°
63°
17
80°
63°
18
77°
62°
19
80°
61°
20
81°
62°
21
82°
58°
22
83°
58°
23
83°
50°
24
77°
53°
25
76°
52°
26
77°
54°
27
76°
61°
28
82°
59°
29
84°
60°
30
77°
57°
1
83°
56°
2
73°
58°
3
73°
57°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in St. Charles
St. Charles's September 2026 forecast shows daily high temperatures ranging from 73° to 87°, with overnight lows between 50° and 67°. The average high for September is 80° with an average low of 61°. AccuWeather's monthly forecast extends further ahead than any other source, with day-by-day RealFeel® Temperatures giving a complete picture of how September weather will actually feel in St. Charles. See also: October | November | December.
