S
M
T
W
T
F
S
30
76°
42°
31
77°
43°
1
76°
38°
2
75°
41°
3
75°
43°
4
76°
37°
5
72°
37°
6
73°
36°
7
72°
40°
8
73°
39°
9
74°
41°
10
73°
35°
11
71°
38°
12
71°
37°
13
71°
37°
14
71°
38°
15
Hist. Avg.
78°
44°
16
Hist. Avg.
78°
44°
17
Hist. Avg.
77°
44°
18
Hist. Avg.
77°
43°
19
Hist. Avg.
76°
43°
20
Hist. Avg.
76°
43°
21
Hist. Avg.
75°
42°
22
Hist. Avg.
75°
42°
23
Hist. Avg.
74°
42°
24
Hist. Avg.
74°
41°
25
Hist. Avg.
74°
41°
26
Hist. Avg.
73°
40°
27
Hist. Avg.
72°
40°
28
Hist. Avg.
72°
40°
29
Hist. Avg.
72°
39°
30
Hist. Avg.
71°
39°
1
Hist. Avg.
71°
38°
2
Hist. Avg.
70°
38°
3
Hist. Avg.
70°
38°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
*Temporarily Unavailable
September Weather in St. Charles
St. Charles's September 2026 forecast shows daily high temperatures ranging from 71° to 77°, with overnight lows between 35° and 43°. The average high for September is 74° with an average low of 39°. 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.
