S
M
T
W
T
F
S
30
93°
63°
31
94°
68°
1
95°
69°
2
98°
68°
3
98°
70°
4
98°
70°
5
89°
69°
6
86°
59°
7
87°
58°
8
90°
61°
9
92°
67°
10
81°
69°
11
80°
67°
12
82°
68°
13
89°
68°
14
78°
53°
15
89°
53°
16
92°
64°
17
93°
70°
18
84°
69°
19
86°
65°
20
83°
68°
21
82°
59°
22
67°
57°
23
71°
61°
24
69°
52°
25
72°
43°
26
75°
46°
27
77°
49°
28
74°
52°
29
78°
52°
30
79°
58°
1
84°
62°
2
82°
62°
3
80°
61°
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 74° to 84°, with overnight lows between 46° and 62°. The average high for September is 79° with an average low of 55°. 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.
