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
90°
81°
12
89°
81°
13
88°
79°
14
88°
79°
15
88°
77°
16
89°
78°
17
93°
76°
18
91°
79°
19
89°
78°
20
90°
78°
21
91°
78°
22
89°
78°
23
90°
78°
24
91°
78°
25
90°
79°
26
89°
76°
27
90°
75°
28
89°
76°
29
87°
77°
30
88°
76°
1
88°
76°
2
87°
77°
3
87°
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 87° to 91°, with overnight lows between 75° and 79°. The average high for September is 89° 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 Guaynabo. See also: October | November | December.
