S
M
T
W
T
F
S
30
96°
79°
31
96°
79°
1
98°
78°
2
98°
79°
3
97°
74°
4
96°
74°
5
92°
77°
6
94°
79°
7
97°
79°
8
97°
78°
9
96°
79°
10
97°
78°
11
97°
78°
12
96°
77°
13
97°
78°
14
97°
77°
15
96°
74°
16
93°
73°
17
92°
76°
18
95°
75°
19
93°
76°
20
92°
77°
21
93°
76°
22
94°
76°
23
91°
75°
24
91°
74°
25
92°
75°
26
93°
75°
27
94°
74°
28
95°
75°
29
92°
74°
30
90°
74°
1
93°
74°
2
90°
74°
3
91°
71°
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 90° to 98°, with overnight lows between 71° and 79°. The average high for September is 94° 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.
