S
M
T
W
T
F
S
30
89°
58°
31
80°
52°
1
71°
46°
2
70°
50°
3
66°
52°
4
75°
46°
5
77°
50°
6
78°
49°
7
88°
51°
8
93°
60°
9
98°
62°
10
102°
59°
11
92°
54°
12
88°
52°
13
87°
51°
14
86°
50°
15
83°
51°
16
86°
54°
17
89°
55°
18
90°
53°
19
87°
50°
20
87°
53°
21
79°
53°
22
79°
52°
23
83°
52°
24
82°
51°
25
81°
47°
26
78°
52°
27
85°
52°
28
85°
53°
29
84°
53°
30
84°
52°
1
85°
52°
2
85°
51°
3
84°
51°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in Clearlake
Clearlake's September 2026 forecast shows daily high temperatures ranging from 78° to 102°, with overnight lows between 47° and 62°. The average high for September is 86° 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 Clearlake. See also: October | November | December.
