S
M
T
W
T
F
S
30
76°
51°
31
72°
55°
1
71°
58°
2
75°
60°
3
72°
52°
4
77°
50°
5
78°
51°
6
80°
53°
7
83°
54°
8
91°
59°
9
88°
58°
10
85°
57°
11
91°
56°
12
87°
56°
13
86°
57°
14
87°
54°
15
84°
56°
16
80°
54°
17
86°
55°
18
86°
53°
19
79°
51°
20
82°
56°
21
83°
53°
22
85°
53°
23
79°
54°
24
78°
49°
25
77°
49°
26
77°
50°
27
76°
49°
28
77°
49°
29
78°
50°
30
77°
53°
1
77°
49°
2
78°
51°
3
83°
55°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in Napa
Napa's September 2026 forecast shows daily high temperatures ranging from 71° to 91°, with overnight lows between 49° and 60°. The average high for September is 81° with an average low of 53°. 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 Napa. See also: October | November | December.
