S
M
T
W
T
F
S
30
72°
55°
31
73°
57°
1
73°
48°
2
68°
59°
3
75°
64°
4
70°
55°
5
72°
50°
6
77°
52°
7
73°
57°
8
66°
54°
9
66°
48°
10
N/A
11
72°
54°
12
69°
63°
13
72°
63°
14
72°
63°
15
72°
52°
16
68°
56°
17
68°
54°
18
65°
54°
19
67°
54°
20
65°
55°
21
66°
54°
22
66°
55°
23
67°
54°
24
68°
52°
25
65°
51°
26
64°
51°
27
66°
53°
28
65°
47°
29
60°
46°
30
60°
46°
1
61°
51°
2
63°
52°
3
63°
51°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
*Temporarily Unavailable
September Weather in Portsmouth
Portsmouth's September 2026 forecast shows daily high temperatures ranging from 60° to 72°, with overnight lows between 46° and 63°. The average high for September is 66° 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.
