S
M
T
W
T
F
S
30
101°
73°
31
102°
75°
1
98°
77°
2
99°
78°
3
96°
77°
4
94°
74°
5
94°
75°
6
96°
73°
7
96°
74°
8
95°
75°
9
94°
74°
10
94°
74°
11
95°
72°
12
93°
73°
13
94°
74°
14
91°
70°
15
89°
74°
16
92°
73°
17
92°
73°
18
91°
72°
19
90°
73°
20
90°
73°
21
87°
72°
22
84°
72°
23
83°
71°
24
84°
71°
25
85°
70°
26
84°
71°
27
87°
70°
28
90°
70°
29
89°
69°
30
89°
69°
1
88°
70°
2
86°
69°
3
87°
69°
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 83° to 99°, with overnight lows between 69° and 78°. The average high for September is 91° with an average low of 72°. 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.
