S
M
T
W
T
F
S
30
84°
70°
31
87°
70°
1
85°
69°
2
89°
69°
3
89°
67°
4
88°
65°
5
82°
69°
6
87°
68°
7
84°
64°
8
80°
62°
9
81°
67°
10
80°
68°
11
86°
67°
12
86°
68°
13
87°
67°
14
86°
66°
15
85°
65°
16
78°
64°
17
80°
57°
18
77°
58°
19
77°
54°
20
76°
55°
21
75°
55°
22
75°
60°
23
76°
59°
24
82°
62°
25
81°
63°
26
81°
61°
27
82°
62°
28
81°
59°
29
80°
58°
30
79°
57°
1
76°
56°
2
78°
58°
3
Hist. Avg.
75°
51°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in St. Louis
St. Louis's September 2026 forecast shows daily high temperatures ranging from 75° to 89°, with overnight lows between 54° and 70°. The average high for September is 82° with an average low of 63°. 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. Louis. See also: October | November | December.
