S
M
T
W
T
F
S
30
88°
64°
31
87°
61°
1
79°
60°
2
79°
57°
3
80°
59°
4
85°
63°
5
83°
64°
6
78°
64°
7
83°
60°
8
85°
61°
9
86°
60°
10
83°
61°
11
86°
62°
12
85°
61°
13
85°
61°
14
84°
60°
15
85°
52°
16
79°
50°
17
75°
50°
18
75°
51°
19
76°
58°
20
81°
58°
21
78°
57°
22
76°
50°
23
80°
52°
24
82°
52°
25
82°
54°
26
81°
56°
27
81°
56°
28
80°
46°
29
79°
47°
30
69°
52°
1
68°
51°
2
70°
53°
3
69°
52°
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 68° to 88°, with overnight lows between 46° and 64°. The average high for September is 80° 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.
