S
M
T
W
T
F
S
30
77°
64°
31
87°
71°
1
91°
72°
2
91°
71°
3
90°
68°
4
84°
64°
5
81°
61°
6
79°
61°
7
80°
59°
8
77°
58°
9
79°
62°
10
76°
58°
11
76°
55°
12
78°
59°
13
80°
58°
14
80°
59°
15
79°
60°
16
79°
59°
17
78°
58°
18
74°
57°
19
78°
58°
20
79°
59°
21
80°
59°
22
79°
58°
23
79°
58°
24
78°
57°
25
77°
56°
26
78°
55°
27
77°
56°
28
77°
55°
29
76°
54°
30
75°
53°
1
74°
53°
2
74°
52°
3
75°
53°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in Dekalb
Dekalb's September 2026 forecast shows daily high temperatures ranging from 74° to 91°, with overnight lows between 52° and 72°. The average high for September is 79° with an average low of 59°. 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 Dekalb. See also: October | November | December.
