S
M
T
W
T
F
S
30
84°
64°
31
83°
57°
1
76°
57°
2
75°
56°
3
75°
56°
4
78°
62°
5
79°
63°
6
78°
64°
7
79°
63°
8
81°
61°
9
82°
61°
10
81°
62°
11
83°
62°
12
82°
61°
13
81°
62°
14
80°
57°
15
82°
50°
16
72°
50°
17
70°
51°
18
71°
50°
19
71°
56°
20
72°
58°
21
70°
57°
22
71°
54°
23
75°
57°
24
78°
56°
25
79°
56°
26
78°
57°
27
77°
55°
28
77°
46°
29
75°
47°
30
64°
50°
1
65°
51°
2
66°
53°
3
65°
48°
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 84°, with overnight lows between 46° and 64°. The average high for September is 76° 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.
