S
M
T
W
T
F
S
30
87°
71°
31
93°
68°
1
96°
71°
2
99°
73°
3
99°
73°
4
97°
73°
5
97°
70°
6
91°
68°
7
88°
68°
8
89°
62°
9
89°
68°
10
90°
69°
11
90°
70°
12
84°
69°
13
86°
68°
14
89°
69°
15
88°
68°
16
89°
66°
17
85°
65°
18
83°
62°
19
80°
59°
20
79°
58°
21
78°
60°
22
85°
64°
23
84°
63°
24
83°
63°
25
83°
62°
26
84°
63°
27
85°
63°
28
84°
62°
29
83°
62°
30
83°
61°
1
82°
62°
2
82°
60°
3
81°
59°
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 78° to 90°, with overnight lows between 58° and 70°. The average high for September is 85° with an average low of 64°. 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.
