S
M
T
W
T
F
S
30
69°
47°
31
78°
43°
1
86°
46°
2
86°
49°
3
79°
53°
4
79°
48°
5
76°
47°
6
65°
52°
7
65°
52°
8
64°
47°
9
76°
45°
10
84°
51°
11
57°
45°
12
60°
42°
13
67°
41°
14
61°
42°
15
68°
41°
16
61°
40°
17
74°
47°
18
72°
52°
19
66°
48°
20
77°
49°
21
79°
50°
22
70°
46°
23
78°
47°
24
76°
49°
25
72°
47°
26
68°
46°
27
62°
47°
28
66°
42°
29
74°
39°
30
59°
38°
1
57°
34°
2
66°
44°
3
67°
40°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in Great Falls
Great Falls's September 2026 forecast shows daily high temperatures ranging from 57° to 79°, with overnight lows between 34° and 52°. The average high for September is 69° with an average low of 45°. 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 Great Falls. See also: October | November | December.
