S
M
T
W
T
F
S
30
82°
41°
31
82°
40°
1
70°
39°
2
68°
39°
3
69°
42°
4
75°
50°
5
80°
51°
6
80°
46°
7
79°
39°
8
68°
42°
9
68°
39°
10
69°
45°
11
69°
39°
12
70°
37°
13
66°
47°
14
71°
50°
15
78°
43°
16
75°
39°
17
65°
38°
18
67°
42°
19
74°
36°
20
67°
36°
21
63°
46°
22
73°
40°
23
66°
35°
24
61°
38°
25
61°
44°
26
71°
41°
27
67°
45°
28
64°
44°
29
71°
38°
30
64°
33°
1
58°
32°
2
56°
33°
3
58°
36°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in Lewistown
Lewistown's September 2026 forecast shows daily high temperatures ranging from 56° to 82°, with overnight lows between 32° and 51°. The average high for September is 69° with an average low of 41°. 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 Lewistown. See also: October | November | December.
