S
M
T
W
T
F
S
30
82°
64°
31
86°
72°
1
91°
73°
2
93°
73°
3
95°
73°
4
84°
72°
5
81°
66°
6
77°
61°
7
79°
61°
8
86°
66°
9
88°
70°
10
81°
68°
11
79°
59°
12
77°
68°
13
84°
57°
14
72°
50°
15
88°
59°
16
86°
70°
17
82°
67°
18
75°
56°
19
77°
66°
20
76°
59°
21
68°
56°
22
66°
58°
23
72°
56°
24
69°
54°
25
70°
52°
26
69°
49°
27
71°
53°
28
74°
52°
29
72°
53°
30
69°
46°
1
73°
55°
2
70°
54°
3
67°
55°
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 66° to 82°, with overnight lows between 46° and 67°. The average high for September is 72° with an average low of 55°. 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.
