S
M
T
W
T
F
S
30
79°
53°
31
76°
52°
1
74°
53°
2
78°
52°
3
81°
53°
4
81°
52°
5
80°
53°
6
80°
52°
7
79°
52°
8
80°
51°
9
79°
51°
10
74°
49°
11
81°
48°
12
77°
50°
13
79°
49°
14
80°
48°
15
78°
46°
16
71°
45°
17
72°
48°
18
76°
49°
19
77°
50°
20
78°
50°
21
78°
49°
22
77°
50°
23
77°
49°
24
76°
45°
25
73°
38°
26
63°
34°
27
60°
38°
28
66°
42°
29
70°
43°
30
71°
33°
1
67°
31°
2
55°
37°
3
62°
42°
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 55° to 81°, with overnight lows between 31° and 53°. The average high for September is 74° with an average low of 47°. 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.
