S
M
T
W
T
F
S
30
81°
68°
31
87°
70°
1
93°
72°
2
94°
72°
3
90°
70°
4
88°
69°
5
83°
67°
6
81°
63°
7
78°
61°
8
75°
60°
9
76°
59°
10
76°
61°
11
75°
54°
12
76°
53°
13
76°
56°
14
75°
53°
15
78°
57°
16
78°
58°
17
77°
58°
18
77°
57°
19
78°
59°
20
79°
59°
21
79°
58°
22
78°
58°
23
78°
57°
24
77°
58°
25
78°
58°
26
78°
56°
27
77°
57°
28
77°
57°
29
76°
56°
30
75°
55°
1
75°
55°
2
74°
54°
3
75°
54°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in Crystal Lake
Crystal Lake's September 2026 forecast shows daily high temperatures ranging from 74° to 94°, with overnight lows between 53° 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 Crystal Lake. See also: October | November | December.
