S
M
T
W
T
F
S
30
70°
56°
31
69°
56°
1
65°
55°
2
64°
54°
3
64°
52°
4
65°
53°
5
64°
51°
6
66°
55°
7
67°
51°
8
68°
52°
9
68°
56°
10
67°
55°
11
63°
55°
12
63°
54°
13
64°
54°
14
63°
49°
15
62°
49°
16
62°
50°
17
63°
49°
18
63°
53°
19
62°
51°
20
61°
48°
21
61°
50°
22
62°
53°
23
65°
53°
24
65°
52°
25
64°
48°
26
62°
47°
27
60°
51°
28
59°
52°
29
60°
51°
30
59°
47°
1
60°
49°
2
58°
47°
3
58°
47°
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 58° to 70°, with overnight lows between 47° and 56°. The average high for September is 63° with an average low of 52°. 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.
