S
M
T
W
T
F
S
30
79°
65°
31
80°
68°
1
90°
68°
2
88°
72°
3
76°
68°
4
79°
66°
5
77°
58°
6
76°
56°
7
78°
54°
8
82°
69°
9
77°
60°
10
76°
50°
11
77°
57°
12
82°
61°
13
76°
54°
14
73°
61°
15
72°
53°
16
73°
51°
17
70°
50°
18
65°
45°
19
65°
46°
20
64°
45°
21
68°
47°
22
66°
52°
23
67°
53°
24
69°
52°
25
74°
52°
26
73°
51°
27
70°
51°
28
74°
53°
29
74°
54°
30
75°
53°
1
74°
51°
2
72°
47°
3
60°
43°
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 60° to 82°, with overnight lows between 43° and 69°. The average high for September is 72° with an average low of 52°. 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.
