S
M
T
W
T
F
S
30
75°
54°
31
81°
50°
1
83°
57°
2
87°
60°
3
84°
54°
4
88°
55°
5
82°
50°
6
78°
52°
7
74°
49°
8
78°
48°
9
77°
47°
10
74°
46°
11
77°
48°
12
78°
45°
13
74°
41°
14
75°
40°
15
79°
47°
16
80°
46°
17
78°
42°
18
71°
39°
19
75°
43°
20
77°
45°
21
76°
42°
22
75°
44°
23
77°
45°
24
77°
44°
25
70°
42°
26
73°
44°
27
74°
43°
28
74°
43°
29
73°
42°
30
73°
43°
1
72°
42°
2
72°
42°
3
70°
41°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in Joliet
Joliet's September 2026 forecast shows daily high temperatures ranging from 70° to 88°, with overnight lows between 39° and 60°. The average high for September is 77° with an average low of 46°. 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 Joliet. See also: October | November | December.
