S
M
T
W
T
F
S
30
77°
56°
31
78°
55°
1
77°
56°
2
76°
55°
3
76°
54°
4
77°
56°
5
79°
59°
6
75°
58°
7
75°
56°
8
80°
53°
9
75°
57°
10
77°
61°
11
80°
59°
12
81°
59°
13
80°
51°
14
75°
57°
15
73°
51°
16
73°
51°
17
70°
57°
18
77°
53°
19
74°
55°
20
72°
48°
21
78°
47°
22
69°
45°
23
76°
55°
24
77°
56°
25
Hist. Avg.
71°
50°
26
Hist. Avg.
71°
50°
27
Hist. Avg.
70°
49°
28
Hist. Avg.
70°
49°
29
Hist. Avg.
69°
48°
30
Hist. Avg.
69°
48°
1
Hist. Avg.
68°
48°
2
Hist. Avg.
68°
47°
3
Hist. Avg.
68°
47°
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 81°, with overnight lows between 45° and 61°. The average high for September is 76° with an average low of 55°. 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.
