S
M
T
W
T
F
S
30
77°
58°
31
76°
57°
1
75°
56°
2
74°
58°
3
75°
60°
4
74°
59°
5
76°
57°
6
75°
58°
7
73°
56°
8
74°
57°
9
72°
56°
10
73°
61°
11
73°
55°
12
75°
55°
13
77°
54°
14
75°
60°
15
75°
59°
16
73°
54°
17
70°
53°
18
71°
53°
19
71°
58°
20
72°
58°
21
75°
57°
22
72°
57°
23
75°
56°
24
74°
54°
25
73°
56°
26
67°
49°
27
73°
49°
28
66°
48°
29
65°
49°
30
68°
51°
1
68°
48°
2
Hist. Avg.
69°
50°
3
Hist. Avg.
68°
50°
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 65° to 77°, with overnight lows between 48° and 61°. The average high for September is 73° with an average low of 55°. 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.
