S
M
T
W
T
F
S
30
78°
61°
31
79°
63°
1
79°
64°
2
80°
57°
3
78°
54°
4
76°
55°
5
75°
55°
6
77°
56°
7
81°
56°
8
82°
61°
9
82°
61°
10
81°
54°
11
76°
57°
12
77°
58°
13
76°
52°
14
75°
53°
15
74°
52°
16
73°
51°
17
75°
57°
18
77°
50°
19
75°
52°
20
74°
52°
21
79°
53°
22
75°
57°
23
79°
57°
24
76°
56°
25
75°
57°
26
79°
56°
27
79°
56°
28
80°
55°
29
79°
55°
30
78°
54°
1
78°
55°
2
79°
47°
3
78°
44°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in Illiana
Illiana's September 2026 forecast shows daily high temperatures ranging from 73° to 82°, with overnight lows between 44° and 64°. The average high for September is 78° 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 Illiana. See also: October | November | December.
