S
M
T
W
T
F
S
30
77°
51°
31
71°
50°
1
70°
51°
2
70°
50°
3
71°
49°
4
70°
49°
5
76°
57°
6
76°
58°
7
76°
56°
8
79°
49°
9
74°
55°
10
76°
56°
11
79°
53°
12
75°
52°
13
77°
57°
14
77°
49°
15
76°
43°
16
67°
42°
17
66°
43°
18
67°
49°
19
70°
50°
20
69°
52°
21
70°
52°
22
70°
51°
23
72°
52°
24
72°
52°
25
68°
51°
26
74°
52°
27
73°
42°
28
73°
38°
29
68°
38°
30
60°
41°
1
59°
37°
2
60°
42°
3
59°
43°
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 59° to 79°, with overnight lows between 37° and 58°. The average high for September is 71° with an average low of 49°. 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.
