S
M
T
W
T
F
S
30
88°
80°
31
94°
79°
1
91°
75°
2
90°
79°
3
90°
80°
4
91°
78°
5
90°
79°
6
90°
78°
7
88°
78°
8
90°
79°
9
90°
79°
10
91°
80°
11
91°
79°
12
90°
80°
13
90°
79°
14
89°
79°
15
89°
79°
16
90°
79°
17
89°
78°
18
88°
76°
19
90°
75°
20
89°
76°
21
90°
77°
22
90°
77°
23
89°
78°
24
87°
77°
25
88°
77°
26
87°
76°
27
87°
75°
28
88°
77°
29
88°
77°
30
85°
76°
1
86°
77°
2
88°
77°
3
87°
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 85° to 91°, with overnight lows between 75° and 80°. The average high for September is 88° with an average low of 77°. 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.
