S
M
T
W
T
F
S
30
90°
72°
31
90°
74°
1
91°
75°
2
90°
70°
3
89°
69°
4
88°
69°
5
87°
70°
6
89°
73°
7
90°
74°
8
92°
74°
9
91°
73°
10
92°
72°
11
92°
72°
12
89°
73°
13
91°
73°
14
93°
68°
15
89°
68°
16
88°
67°
17
87°
68°
18
88°
67°
19
88°
70°
20
89°
70°
21
86°
69°
22
86°
70°
23
87°
70°
24
86°
69°
25
86°
69°
26
87°
68°
27
87°
69°
28
86°
69°
29
85°
68°
30
85°
68°
1
86°
67°
2
87°
67°
3
88°
63°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in Mission Valley
Mission Valley's September 2026 forecast shows daily high temperatures ranging from 85° to 93°, with overnight lows between 63° and 75°. The average high for September is 88° with an average low of 70°. 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 Mission Valley. See also: October | November | December.
