S
M
T
W
T
F
S
30
77°
59°
31
71°
60°
1
78°
62°
2
76°
59°
3
75°
58°
4
79°
60°
5
80°
57°
6
79°
59°
7
73°
56°
8
78°
57°
9
75°
50°
10
71°
55°
11
72°
54°
12
75°
54°
13
76°
55°
14
76°
55°
15
75°
54°
16
76°
53°
17
68°
52°
18
74°
52°
19
71°
51°
20
69°
54°
21
73°
53°
22
73°
54°
23
74°
52°
24
69°
49°
25
61°
45°
26
64°
46°
27
68°
47°
28
70°
50°
29
71°
50°
30
71°
49°
1
70°
49°
2
70°
50°
3
68°
49°
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 61° to 80°, with overnight lows between 45° and 62°. The average high for September is 73° 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 Cornwall. See also: October | November | December.
