S
M
T
W
T
F
S
30
89°
74°
31
91°
75°
1
90°
75°
2
90°
74°
3
89°
75°
4
90°
76°
5
90°
75°
6
89°
75°
7
88°
74°
8
88°
74°
9
89°
75°
10
88°
74°
11
86°
74°
12
88°
75°
13
89°
74°
14
89°
73°
15
88°
71°
16
85°
72°
17
87°
74°
18
88°
73°
19
88°
72°
20
87°
73°
21
87°
74°
22
88°
74°
23
86°
73°
24
86°
73°
25
84°
71°
26
86°
73°
27
84°
74°
28
85°
72°
29
86°
72°
30
85°
73°
1
86°
71°
2
87°
70°
3
86°
73°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in Port St. John
Port St. John's September 2026 forecast shows daily high temperatures ranging from 84° to 91°, with overnight lows between 70° and 76°. The average high for September is 87° with an average low of 73°. 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 St. John. See also: October | November | December.
