S
M
T
W
T
F
S
30
82°
72°
31
83°
72°
1
82°
73°
2
84°
72°
3
84°
73°
4
83°
72°
5
82°
74°
6
83°
73°
7
82°
72°
8
83°
73°
9
83°
73°
10
82°
72°
11
82°
72°
12
83°
73°
13
82°
72°
14
82°
73°
15
83°
73°
16
82°
74°
17
84°
72°
18
82°
73°
19
82°
72°
20
83°
71°
21
84°
74°
22
85°
73°
23
84°
72°
24
84°
71°
25
83°
72°
26
84°
72°
27
84°
73°
28
83°
72°
29
84°
73°
30
84°
72°
1
85°
72°
2
85°
73°
3
84°
73°
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 82° to 85°, with overnight lows between 71° and 74°. The average high for September is 83° 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 San Juan. See also: October | November | December.
