S
M
T
W
T
F
S
30
91°
54°
31
92°
53°
1
91°
52°
2
89°
51°
3
89°
52°
4
91°
55°
5
91°
55°
6
90°
52°
7
88°
54°
8
85°
54°
9
88°
50°
10
87°
48°
11
85°
48°
12
84°
49°
13
84°
46°
14
83°
46°
15
82°
53°
16
82°
49°
17
88°
48°
18
86°
47°
19
83°
49°
20
85°
48°
21
86°
49°
22
86°
51°
23
84°
52°
24
80°
51°
25
Hist. Avg.
88°
47°
26
Hist. Avg.
88°
46°
27
Hist. Avg.
88°
46°
28
Hist. Avg.
87°
46°
29
Hist. Avg.
87°
46°
30
Hist. Avg.
87°
46°
1
Hist. Avg.
86°
46°
2
Hist. Avg.
86°
46°
3
Hist. Avg.
86°
45°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
*Temporarily Unavailable
September Weather in Clearlake
Clearlake's September 2026 forecast shows daily high temperatures ranging from 80° to 92°, with overnight lows between 46° and 55°. The average high for September is 87° 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 Clearlake. See also: October | November | December.
