S
M
T
W
T
F
S
30
83°
58°
31
75°
57°
1
68°
60°
2
70°
62°
3
72°
62°
4
81°
61°
5
72°
56°
6
72°
52°
7
76°
55°
8
77°
56°
9
72°
63°
10
76°
54°
11
71°
53°
12
71°
55°
13
72°
56°
14
77°
59°
15
79°
57°
16
77°
51°
17
75°
55°
18
66°
50°
19
73°
54°
20
72°
54°
21
69°
53°
22
70°
53°
23
70°
52°
24
69°
52°
25
67°
51°
26
70°
53°
27
71°
54°
28
70°
51°
29
62°
48°
30
65°
49°
1
62°
47°
2
61°
47°
3
60°
49°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in Portsmouth
Portsmouth's September 2026 forecast shows daily high temperatures ranging from 60° to 81°, with overnight lows between 47° and 63°. The average high for September is 71° with an average low of 54°. 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 Portsmouth. See also: October | November | December.
