S
M
T
W
T
F
S
30
82°
53°
31
75°
58°
1
75°
59°
2
76°
59°
3
81°
63°
4
84°
59°
5
83°
52°
6
75°
51°
7
75°
51°
8
73°
53°
9
78°
58°
10
75°
53°
11
72°
48°
12
71°
47°
13
73°
51°
14
72°
48°
15
70°
47°
16
70°
46°
17
69°
46°
18
68°
47°
19
68°
46°
20
69°
46°
21
69°
47°
22
70°
49°
23
71°
52°
24
72°
53°
25
75°
54°
26
75°
46°
27
74°
45°
28
66°
53°
29
66°
51°
30
73°
50°
1
71°
51°
2
68°
49°
3
64°
48°
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 64° to 84°, with overnight lows between 45° and 63°. The average high for September is 73° with an average low of 51°. 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.
