S
M
T
W
T
F
S
30
74°
52°
31
78°
54°
1
70°
59°
2
67°
59°
3
71°
60°
4
76°
56°
5
69°
48°
6
73°
48°
7
72°
50°
8
73°
49°
9
75°
55°
10
75°
53°
11
70°
51°
12
73°
51°
13
71°
48°
14
68°
47°
15
67°
44°
16
69°
50°
17
73°
47°
18
64°
43°
19
65°
40°
20
69°
46°
21
72°
50°
22
73°
50°
23
73°
48°
24
71°
47°
25
70°
45°
26
70°
46°
27
71°
47°
28
71°
45°
29
68°
40°
30
59°
37°
1
58°
35°
2
62°
44°
3
68°
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 58° to 76°, with overnight lows between 35° and 60°. The average high for September is 70° with an average low of 48°. 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.
