S
M
T
W
T
F
S
30
99°
73°
31
93°
68°
1
91°
63°
2
90°
59°
3
88°
61°
4
88°
61°
5
95°
59°
6
76°
64°
7
90°
70°
8
100°
70°
9
106°
75°
10
104°
79°
11
99°
77°
12
97°
70°
13
94°
64°
14
93°
63°
15
90°
61°
16
90°
62°
17
93°
62°
18
97°
64°
19
98°
65°
20
97°
68°
21
93°
66°
22
90°
64°
23
88°
63°
24
86°
62°
25
90°
63°
26
94°
66°
27
89°
59°
28
86°
54°
29
86°
58°
30
84°
59°
1
83°
57°
2
82°
55°
3
82°
57°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in San Bernardino
San Bernardino's September 2026 forecast shows daily high temperatures ranging from 82° to 98°, with overnight lows between 54° and 68°. The average high for September is 90° with an average low of 62°. 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 San Bernardino. See also: October | November | December.
