S
M
T
W
T
F
S
30
85°
82°
31
89°
82°
1
87°
81°
2
89°
82°
3
88°
82°
4
88°
82°
5
88°
82°
6
87°
82°
7
88°
82°
8
88°
82°
9
87°
79°
10
89°
82°
11
95°
83°
12
93°
82°
13
90°
81°
14
93°
82°
15
92°
81°
16
94°
78°
17
90°
76°
18
91°
75°
19
90°
74°
20
89°
74°
21
90°
74°
22
91°
73°
23
90°
75°
24
88°
73°
25
88°
76°
26
89°
75°
27
87°
76°
28
88°
76°
29
89°
75°
30
89°
76°
1
88°
75°
2
87°
75°
3
85°
74°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in Port Isabel
Port Isabel's September 2026 forecast shows daily high temperatures ranging from 85° to 95°, with overnight lows between 73° and 83°. The average high for September is 90° with an average low of 76°. 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 Port Isabel. See also: October | November | December.
