S
M
T
W
T
F
S
30
96°
72°
31
91°
68°
1
90°
64°
2
88°
63°
3
86°
63°
4
88°
63°
5
95°
63°
6
77°
66°
7
89°
72°
8
100°
75°
9
109°
80°
10
102°
80°
11
97°
76°
12
93°
70°
13
90°
69°
14
89°
66°
15
83°
62°
16
84°
63°
17
86°
60°
18
86°
59°
19
91°
62°
20
86°
66°
21
85°
67°
22
86°
64°
23
84°
65°
24
84°
64°
25
85°
66°
26
89°
66°
27
90°
65°
28
85°
60°
29
87°
62°
30
84°
62°
1
82°
61°
2
81°
62°
3
81°
61°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in Rancho Cucamonga
Rancho Cucamonga's September 2026 forecast shows daily high temperatures ranging from 81° to 91°, with overnight lows between 59° and 67°. The average high for September is 85° with an average low of 63°. 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 Rancho Cucamonga. See also: October | November | December.
