S
M
T
W
T
F
S
30
82°
51°
31
82°
55°
1
84°
59°
2
88°
60°
3
88°
51°
4
80°
55°
5
81°
51°
6
84°
49°
7
81°
50°
8
80°
52°
9
83°
52°
10
85°
54°
11
87°
58°
12
88°
59°
13
89°
56°
14
88°
50°
15
81°
51°
16
81°
52°
17
82°
54°
18
82°
56°
19
86°
53°
20
86°
53°
21
85°
55°
22
81°
49°
23
77°
46°
24
76°
45°
25
75°
45°
26
74°
47°
27
75°
50°
28
77°
49°
29
82°
45°
30
75°
45°
1
Hist. Avg.
77°
51°
2
Hist. Avg.
76°
51°
3
Hist. Avg.
76°
51°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in Grass Valley
Grass Valley's September 2026 forecast shows daily high temperatures ranging from 74° to 89°, with overnight lows between 45° and 60°. The average high for September is 82° with an average low of 52°. 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 Grass Valley. See also: October | November | December.
