S
M
T
W
T
F
S
30
88°
75°
31
90°
75°
1
89°
77°
2
88°
75°
3
90°
75°
4
90°
74°
5
90°
74°
6
90°
74°
7
90°
76°
8
91°
75°
9
89°
75°
10
82°
75°
11
88°
73°
12
86°
73°
13
94°
73°
14
92°
74°
15
94°
72°
16
90°
76°
17
91°
72°
18
90°
69°
19
94°
69°
20
93°
72°
21
91°
72°
22
90°
71°
23
92°
72°
24
88°
72°
25
86°
66°
26
87°
69°
27
89°
68°
28
89°
69°
29
90°
71°
30
89°
72°
1
89°
72°
2
90°
71°
3
88°
68°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in Saint Charles
Saint Charles's September 2026 forecast shows daily high temperatures ranging from 86° to 90°, with overnight lows between 66° and 72°. The average high for September is 89° with an average low of 70°. 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 Saint Charles. See also: October | November | December.
