S
M
T
W
T
F
S
30
81°
60°
31
77°
61°
1
78°
61°
2
82°
56°
3
82°
51°
4
74°
52°
5
73°
59°
6
79°
55°
7
78°
51°
8
72°
53°
9
71°
55°
10
73°
58°
11
75°
57°
12
80°
58°
13
80°
58°
14
79°
53°
15
78°
50°
16
70°
52°
17
70°
48°
18
71°
48°
19
69°
45°
20
68°
45°
21
67°
47°
22
68°
54°
23
69°
47°
24
71°
53°
25
73°
54°
26
70°
54°
27
75°
55°
28
75°
51°
29
74°
49°
30
67°
49°
1
68°
50°
2
73°
53°
3
66°
43°
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 66° to 82°, with overnight lows between 43° and 61°. The average high for September is 74° with an average low of 53°. 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.
