S
M
T
W
T
F
S
30
83°
70°
31
89°
70°
1
96°
73°
2
96°
77°
3
89°
73°
4
94°
73°
5
79°
69°
6
78°
64°
7
80°
61°
8
86°
61°
9
79°
71°
10
76°
59°
11
82°
56°
12
90°
62°
13
72°
53°
14
70°
49°
15
83°
66°
16
72°
63°
17
74°
64°
18
72°
64°
19
76°
65°
20
69°
59°
21
66°
55°
22
63°
55°
23
65°
56°
24
67°
54°
25
69°
55°
26
71°
54°
27
70°
54°
28
72°
53°
29
69°
53°
30
70°
55°
1
70°
54°
2
69°
48°
3
64°
54°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in Northbrook
Northbrook's September 2026 forecast shows daily high temperatures ranging from 63° to 76°, with overnight lows between 48° and 65°. The average high for September is 69° 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 Northbrook. See also: October | November | December.
