S
M
T
W
T
F
S
30
78°
51°
31
74°
48°
1
71°
51°
2
72°
49°
3
72°
50°
4
73°
49°
5
70°
49°
6
71°
54°
7
72°
53°
8
72°
51°
9
73°
48°
10
71°
48°
11
70°
49°
12
70°
50°
13
69°
49°
14
70°
47°
15
70°
53°
16
75°
46°
17
74°
47°
18
73°
47°
19
69°
52°
20
75°
50°
21
75°
50°
22
Hist. Avg.
71°
49°
23
Hist. Avg.
70°
49°
24
Hist. Avg.
70°
49°
25
Hist. Avg.
70°
48°
26
Hist. Avg.
69°
48°
27
Hist. Avg.
69°
48°
28
Hist. Avg.
68°
47°
29
Hist. Avg.
68°
47°
30
Hist. Avg.
68°
47°
1
Hist. Avg.
67°
46°
2
Hist. Avg.
67°
46°
3
Hist. Avg.
66°
46°
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 69° to 78°, with overnight lows between 46° and 54°. The average high for September is 72° with an average low of 50°. 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.
