S
M
T
W
T
F
S
30
89°
57°
31
78°
59°
1
76°
58°
2
78°
57°
3
76°
58°
4
79°
54°
5
81°
55°
6
86°
57°
7
86°
62°
8
91°
61°
9
95°
61°
10
92°
59°
11
100°
59°
12
91°
61°
13
92°
61°
14
92°
61°
15
91°
61°
16
88°
60°
17
91°
60°
18
90°
58°
19
83°
55°
20
86°
56°
21
89°
58°
22
90°
60°
23
87°
55°
24
81°
52°
25
79°
53°
26
79°
52°
27
78°
51°
28
79°
51°
29
80°
52°
30
80°
54°
1
78°
50°
2
79°
51°
3
83°
54°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in Riverside
Riverside's September 2026 forecast shows daily high temperatures ranging from 76° to 100°, with overnight lows between 50° and 62°. The average high for September is 85° with an average low of 57°. 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 Riverside. See also: October | November | December.
