S
M
T
W
T
F
S
30
74°
58°
31
70°
56°
1
78°
64°
2
75°
59°
3
75°
53°
4
75°
51°
5
74°
52°
6
74°
49°
7
80°
52°
8
73°
60°
9
75°
58°
10
66°
44°
11
73°
39°
12
74°
52°
13
66°
44°
14
62°
41°
15
63°
47°
16
70°
48°
17
72°
47°
18
60°
39°
19
65°
42°
20
67°
40°
21
59°
41°
22
65°
48°
23
65°
49°
24
66°
48°
25
68°
50°
26
69°
50°
27
70°
51°
28
67°
48°
29
63°
42°
30
64°
48°
1
62°
48°
2
58°
44°
3
59°
46°
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 58° to 72°, with overnight lows between 39° and 51°. The average high for September is 65° with an average low of 46°. 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.
