S
M
T
W
T
F
S
30
74°
56°
31
73°
56°
1
61°
43°
2
58°
45°
3
53°
49°
4
52°
44°
5
58°
46°
6
62°
48°
7
68°
48°
8
75°
57°
9
84°
65°
10
80°
65°
11
75°
62°
12
73°
52°
13
63°
50°
14
70°
52°
15
69°
53°
16
64°
48°
17
61°
49°
18
69°
56°
19
76°
59°
20
73°
60°
21
76°
60°
22
77°
59°
23
80°
60°
24
75°
59°
25
74°
60°
26
72°
56°
27
71°
55°
28
68°
50°
29
64°
52°
30
79°
43°
1
74°
47°
2
69°
47°
3
74°
47°
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 61° to 80°, with overnight lows between 43° and 60°. The average high for September is 72° with an average low of 54°. 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.
