S
M
T
W
T
F
S
30
96°
72°
31
99°
73°
1
100°
79°
2
100°
82°
3
99°
82°
4
100°
81°
5
101°
81°
6
90°
73°
7
87°
65°
8
93°
65°
9
93°
72°
10
80°
71°
11
83°
69°
12
92°
71°
13
86°
66°
14
88°
63°
15
98°
76°
16
94°
75°
17
99°
79°
18
98°
75°
19
97°
79°
20
92°
70°
21
73°
66°
22
72°
61°
23
70°
56°
24
70°
60°
25
76°
59°
26
70°
57°
27
75°
57°
28
76°
56°
29
82°
65°
30
81°
66°
1
83°
63°
2
77°
60°
3
75°
56°
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 70° to 83°, with overnight lows between 56° and 66°. The average high for September is 77° with an average low of 60°. 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.
