S
M
T
W
T
F
S
30
87°
78°
31
86°
77°
1
87°
76°
2
86°
77°
3
86°
77°
4
87°
78°
5
87°
78°
6
88°
76°
7
86°
76°
8
86°
77°
9
87°
77°
10
87°
76°
11
86°
77°
12
87°
77°
13
88°
76°
14
89°
74°
15
89°
75°
16
90°
75°
17
89°
76°
18
89°
76°
19
90°
75°
20
90°
77°
21
89°
76°
22
90°
76°
23
90°
75°
24
89°
76°
25
90°
76°
26
89°
74°
27
90°
75°
28
89°
76°
29
90°
75°
30
89°
76°
1
89°
76°
2
90°
75°
3
90°
77°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in Guaynabo
Guaynabo's September 2026 forecast shows daily high temperatures ranging from 86° to 90°, with overnight lows between 74° and 78°. The average high for September is 88° 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 Guaynabo. See also: October | November | December.
