S
M
T
W
T
F
S
30
91°
76°
31
92°
76°
1
91°
77°
2
92°
76°
3
89°
77°
4
91°
76°
5
89°
77°
6
90°
76°
7
91°
77°
8
90°
76°
9
89°
77°
10
90°
77°
11
89°
76°
12
88°
76°
13
88°
77°
14
89°
76°
15
88°
76°
16
88°
77°
17
89°
76°
18
88°
76°
19
88°
77°
20
90°
77°
21
89°
76°
22
90°
77°
23
89°
76°
24
88°
76°
25
88°
75°
26
89°
76°
27
88°
76°
28
88°
75°
29
89°
76°
30
88°
76°
1
88°
75°
2
89°
76°
3
88°
76°
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 92°, with overnight lows between 75° and 77°. 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.
