S
M
T
W
T
F
S
30
90°
77°
31
90°
78°
1
92°
78°
2
92°
77°
3
91°
73°
4
91°
73°
5
87°
77°
6
88°
77°
7
92°
76°
8
92°
78°
9
91°
77°
10
92°
77°
11
91°
76°
12
91°
77°
13
90°
77°
14
91°
76°
15
91°
74°
16
88°
73°
17
88°
75°
18
90°
76°
19
88°
76°
20
87°
75°
21
89°
75°
22
90°
74°
23
86°
75°
24
86°
74°
25
87°
74°
26
89°
75°
27
89°
75°
28
90°
74°
29
87°
74°
30
85°
73°
1
88°
74°
2
85°
74°
3
86°
71°
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 92°, with overnight lows between 71° and 78°. The average high for September is 89° with an average low of 75°. 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.
