S
M
T
W
T
F
S
30
67°
49°
31
74°
47°
1
83°
57°
2
83°
50°
3
80°
48°
4
81°
48°
5
74°
50°
6
75°
53°
7
75°
49°
8
74°
48°
9
71°
49°
10
72°
47°
11
76°
48°
12
73°
46°
13
70°
43°
14
61°
40°
15
76°
49°
16
77°
48°
17
71°
46°
18
65°
44°
19
73°
47°
20
75°
47°
21
69°
44°
22
69°
46°
23
75°
48°
24
74°
47°
25
61°
45°
26
70°
45°
27
72°
46°
28
70°
46°
29
71°
45°
30
70°
45°
1
71°
44°
2
68°
45°
3
67°
44°
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 61° to 83°, with overnight lows between 40° and 57°. The average high for September is 72° with an average low of 47°. 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.
