S
M
T
W
T
F
S
30
91°
64°
31
90°
64°
1
87°
63°
2
89°
62°
3
91°
62°
4
90°
64°
5
91°
64°
6
92°
65°
7
92°
65°
8
89°
64°
9
86°
64°
10
87°
63°
11
87°
64°
12
88°
66°
13
89°
64°
14
91°
66°
15
90°
65°
16
90°
63°
17
89°
62°
18
87°
65°
19
89°
62°
20
86°
63°
21
Hist. Avg.
87°
60°
22
Hist. Avg.
86°
60°
23
Hist. Avg.
86°
60°
24
Hist. Avg.
86°
60°
25
Hist. Avg.
86°
60°
26
Hist. Avg.
86°
59°
27
Hist. Avg.
86°
59°
28
Hist. Avg.
86°
59°
29
Hist. Avg.
86°
59°
30
Hist. Avg.
86°
58°
1
Hist. Avg.
86°
58°
2
Hist. Avg.
86°
58°
3
Hist. Avg.
86°
58°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
*Temporarily Unavailable
September Weather in Lake Forest
Lake Forest's September 2026 forecast shows daily high temperatures ranging from 86° to 92°, with overnight lows between 62° and 66°. The average high for September is 89° with an average low of 64°. 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 Lake Forest. See also: October | November | December.
