S
M
T
W
T
F
S
30
89°
76°
31
90°
78°
1
91°
77°
2
90°
77°
3
91°
76°
4
90°
77°
5
89°
78°
6
89°
77°
7
90°
76°
8
89°
76°
9
89°
77°
10
90°
76°
11
89°
76°
12
88°
77°
13
88°
76°
14
89°
76°
15
89°
75°
16
91°
76°
17
90°
75°
18
89°
76°
19
88°
75°
20
89°
76°
21
89°
75°
22
90°
75°
23
88°
76°
24
89°
76°
25
89°
75°
26
88°
75°
27
89°
76°
28
89°
75°
29
90°
76°
30
90°
76°
1
89°
75°
2
88°
76°
3
89°
75°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in San Juan
San Juan's September 2026 forecast shows daily high temperatures ranging from 88° to 91°, with overnight lows between 75° and 78°. The average high for September is 89° 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 San Juan. See also: October | November | December.
