S
M
T
W
T
F
S
30
83°
63°
31
84°
64°
1
86°
65°
2
88°
68°
3
87°
67°
4
88°
66°
5
87°
62°
6
82°
61°
7
83°
64°
8
84°
65°
9
83°
66°
10
82°
65°
11
86°
64°
12
87°
65°
13
86°
65°
14
86°
66°
15
85°
65°
16
85°
64°
17
84°
64°
18
85°
61°
19
84°
61°
20
83°
56°
21
81°
61°
22
79°
61°
23
80°
60°
24
83°
56°
25
82°
55°
26
81°
59°
27
82°
60°
28
81°
57°
29
80°
58°
30
80°
58°
1
81°
56°
2
80°
57°
3
75°
58°
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 75° to 88°, with overnight lows between 55° and 68°. The average high for September is 83° with an average low of 62°. 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.
