S
M
T
W
T
F
S
30
67°
42°
31
72°
27°
1
68°
40°
2
68°
41°
3
66°
39°
4
70°
36°
5
73°
36°
6
75°
30°
7
57°
41°
8
63°
27°
9
68°
25°
10
74°
45°
11
70°
40°
12
70°
42°
13
68°
35°
14
59°
28°
15
64°
36°
16
69°
37°
17
70°
39°
18
73°
42°
19
71°
41°
20
65°
40°
21
66°
36°
22
65°
39°
23
64°
35°
24
61°
37°
25
54°
35°
26
55°
34°
27
64°
38°
28
57°
30°
29
55°
34°
30
54°
28°
1
58°
36°
2
60°
36°
3
62°
38°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in Yellowstone National Park
Yellowstone National Park's September 2026 forecast shows daily high temperatures ranging from 54° to 74°, with overnight lows between 28° and 45°. The average high for September is 64° with an average low of 37°. 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 Yellowstone National Park. See also: October | November | December.
