S
M
T
W
T
F
S
30
83°
45°
31
75°
42°
1
67°
43°
2
68°
44°
3
71°
48°
4
79°
53°
5
79°
54°
6
78°
47°
7
72°
43°
8
66°
45°
9
65°
43°
10
66°
50°
11
69°
42°
12
65°
41°
13
64°
50°
14
72°
52°
15
74°
45°
16
69°
42°
17
63°
45°
18
66°
44°
19
72°
38°
20
62°
37°
21
60°
37°
22
61°
35°
23
59°
35°
24
57°
43°
25
59°
45°
26
66°
40°
27
62°
45°
28
58°
39°
29
61°
40°
30
59°
38°
1
57°
37°
2
57°
38°
3
62°
43°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in Grantham
Grantham's September 2026 forecast shows daily high temperatures ranging from 57° to 83°, with overnight lows between 35° and 54°. The average high for September is 66° with an average low of 43°. 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 Grantham. See also: October | November | December.
