S
M
T
W
T
F
S
30
81°
67°
31
84°
67°
1
89°
65°
2
86°
64°
3
87°
71°
4
90°
72°
5
76°
69°
6
73°
67°
7
74°
65°
8
79°
64°
9
80°
60°
10
78°
54°
11
79°
61°
12
72°
51°
13
64°
47°
14
62°
56°
15
66°
51°
16
64°
51°
17
69°
51°
18
67°
51°
19
65°
49°
20
66°
50°
21
71°
53°
22
71°
53°
23
70°
51°
24
68°
44°
25
73°
52°
26
72°
51°
27
72°
51°
28
71°
50°
29
67°
49°
30
70°
47°
1
62°
47°
2
66°
46°
3
65°
47°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in Waltham
Waltham's September 2026 forecast shows daily high temperatures ranging from 62° to 79°, with overnight lows between 44° and 61°. The average high for September is 68° with an average low of 50°. 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 Waltham. See also: October | November | December.
