S
M
T
W
T
F
S
30
69°
61°
31
74°
63°
1
80°
66°
2
81°
61°
3
76°
54°
4
74°
52°
5
73°
52°
6
71°
53°
7
70°
50°
8
67°
49°
9
66°
51°
10
71°
51°
11
65°
50°
12
66°
50°
13
66°
48°
14
67°
46°
15
68°
51°
16
71°
51°
17
70°
47°
18
64°
46°
19
67°
50°
20
71°
52°
21
71°
52°
22
70°
51°
23
71°
50°
24
69°
49°
25
69°
48°
26
70°
50°
27
69°
49°
28
69°
48°
29
67°
46°
30
62°
45°
1
62°
46°
2
66°
48°
3
67°
46°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in Grand Valley
Grand Valley's September 2026 forecast shows daily high temperatures ranging from 62° to 81°, with overnight lows between 45° and 66°. The average high for September is 69° with an average low of 50°. 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 Grand Valley. See also: October | November | December.
