S
M
T
W
T
F
S
30
83°
69°
31
86°
69°
1
93°
75°
2
96°
74°
3
91°
72°
4
89°
72°
5
85°
70°
6
83°
65°
7
77°
62°
8
76°
64°
9
77°
63°
10
78°
63°
11
75°
58°
12
77°
57°
13
76°
59°
14
77°
56°
15
79°
61°
16
79°
62°
17
78°
61°
18
78°
62°
19
79°
62°
20
80°
61°
21
80°
61°
22
79°
60°
23
79°
61°
24
78°
61°
25
79°
60°
26
77°
60°
27
78°
59°
28
77°
59°
29
76°
58°
30
75°
58°
1
75°
57°
2
74°
57°
3
75°
56°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in Mount Prospect
Mount Prospect's September 2026 forecast shows daily high temperatures ranging from 74° to 96°, with overnight lows between 56° and 75°. The average high for September is 80° with an average low of 62°. 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 Mount Prospect. See also: October | November | December.
