S
M
T
W
T
F
S
30
71°
52°
31
73°
46°
1
74°
43°
2
68°
44°
3
67°
46°
4
72°
53°
5
71°
49°
6
74°
44°
7
68°
44°
8
66°
51°
9
66°
50°
10
71°
50°
11
71°
49°
12
65°
51°
13
67°
47°
14
64°
43°
15
62°
41°
16
62°
41°
17
63°
49°
18
66°
49°
19
69°
47°
20
71°
48°
21
69°
44°
22
67°
41°
23
61°
39°
24
60°
38°
25
59°
37°
26
58°
39°
27
Hist. Avg.
65°
46°
28
Hist. Avg.
65°
45°
29
Hist. Avg.
65°
45°
30
Hist. Avg.
64°
45°
1
Hist. Avg.
64°
44°
2
Hist. Avg.
63°
44°
3
Hist. Avg.
63°
43°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
*Temporarily Unavailable
September Weather in Grand Valley
Grand Valley's September 2026 forecast shows daily high temperatures ranging from 58° to 74°, with overnight lows between 37° and 53°. The average high for September is 67° with an average low of 46°. 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.
