S
M
T
W
T
F
S
30
56°
42°
31
69°
44°
1
61°
48°
2
57°
40°
3
53°
39°
4
59°
42°
5
54°
46°
6
61°
39°
7
53°
46°
8
70°
43°
9
72°
51°
10
60°
47°
11
58°
43°
12
60°
46°
13
48°
41°
14
46°
43°
15
50°
43°
16
64°
44°
17
71°
48°
18
63°
48°
19
69°
47°
20
73°
56°
21
70°
47°
22
59°
46°
23
52°
37°
24
57°
38°
25
41°
29°
26
44°
32°
27
49°
33°
28
55°
40°
29
53°
39°
30
52°
36°
1
50°
38°
2
51°
37°
3
50°
39°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in Mount Rainier
Mount Rainier's September 2026 forecast shows daily high temperatures ranging from 41° to 57°, with overnight lows between 29° and 40°. The average high for September is 50° with an average low of 36°. 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 Mount Rainier. See also: October | November | December.
