S
M
T
W
T
F
S
30
82°
61°
31
77°
56°
1
75°
56°
2
74°
57°
3
74°
55°
4
75°
57°
5
76°
63°
6
76°
63°
7
79°
63°
8
81°
61°
9
81°
61°
10
77°
62°
11
82°
62°
12
81°
61°
13
81°
62°
14
77°
59°
15
81°
50°
16
72°
49°
17
71°
49°
18
71°
50°
19
72°
53°
20
70°
58°
21
75°
57°
22
70°
56°
23
76°
58°
24
77°
57°
25
76°
57°
26
78°
58°
27
78°
51°
28
77°
45°
29
74°
45°
30
65°
50°
1
64°
46°
2
66°
51°
3
64°
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 64° to 82°, with overnight lows between 45° and 63°. The average high for September is 75° with an average low of 56°. 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.
