S
M
T
W
T
F
S
30
83°
58°
31
65°
51°
1
67°
48°
2
68°
46°
3
71°
47°
4
65°
57°
5
58°
53°
6
56°
52°
7
57°
53°
8
61°
50°
9
61°
54°
10
70°
55°
11
61°
52°
12
62°
52°
13
67°
57°
14
67°
55°
15
68°
54°
16
68°
51°
17
65°
51°
18
66°
49°
19
63°
51°
20
65°
41°
21
60°
51°
22
61°
52°
23
61°
51°
24
63°
50°
25
59°
50°
26
64°
49°
27
57°
49°
28
58°
48°
29
64°
50°
30
64°
49°
1
63°
50°
2
64°
49°
3
63°
50°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in Cornwall
Cornwall's September 2026 forecast shows daily high temperatures ranging from 57° to 70°, with overnight lows between 41° and 57°. The average high for September is 63° 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 Cornwall. See also: October | November | December.
