S
M
T
W
T
F
S
30
75°
58°
31
77°
62°
1
75°
65°
2
80°
57°
3
76°
54°
4
73°
55°
5
72°
54°
6
73°
58°
7
78°
59°
8
80°
63°
9
81°
62°
10
80°
55°
11
73°
61°
12
73°
57°
13
75°
53°
14
72°
53°
15
71°
52°
16
70°
51°
17
72°
59°
18
75°
49°
19
70°
53°
20
70°
49°
21
72°
52°
22
70°
57°
23
75°
58°
24
77°
57°
25
73°
58°
26
76°
57°
27
75°
57°
28
77°
54°
29
74°
55°
30
73°
57°
1
75°
54°
2
76°
46°
3
73°
44°
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 70° to 81°, with overnight lows between 44° and 65°. The average high for September is 74° with an average low of 56°. 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.
