S
M
T
W
T
F
S
30
81°
32°
31
79°
27°
1
68°
24°
2
65°
26°
3
67°
27°
4
74°
34°
5
76°
35°
6
69°
29°
7
73°
23°
8
64°
26°
9
64°
24°
10
65°
31°
11
67°
25°
12
64°
24°
13
63°
34°
14
69°
38°
15
75°
26°
16
66°
23°
17
61°
24°
18
64°
25°
19
70°
24°
20
71°
29°
21
70°
35°
22
70°
34°
23
60°
31°
24
59°
31°
25
65°
34°
26
68°
29°
27
63°
36°
28
65°
33°
29
63°
33°
30
59°
25°
1
55°
22°
2
52°
21°
3
56°
27°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in West Yellowstone
West Yellowstone's September 2026 forecast shows daily high temperatures ranging from 52° to 81°, with overnight lows between 21° and 38°. The average high for September is 66° with an average low of 29°. 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 West Yellowstone. See also: October | November | December.
