S
M
T
W
T
F
S
26
63°
55°
27
73°
54°
28
67°
52°
29
73°
49°
30
72°
49°
31
78°
50°
1
73°
55°
2
70°
49°
3
77°
48°
4
79°
51°
5
79°
53°
6
79°
53°
7
78°
51°
8
72°
50°
9
66°
54°
10
66°
54°
11
69°
49°
12
73°
53°
13
72°
50°
14
68°
51°
15
67°
51°
16
68°
52°
17
72°
51°
18
74°
50°
19
71°
51°
20
79°
50°
21
80°
53°
22
72°
56°
23
70°
51°
24
76°
54°
25
77°
54°
26
68°
53°
27
68°
52°
28
69°
52°
29
69°
51°
30
68°
50°
31
70°
49°
1
69°
49°
2
69°
52°
3
71°
51°
4
72°
52°
5
71°
49°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
August Weather in San Juan Island
San Juan Island's August 2026 forecast shows daily high temperatures ranging from 68° to 77°, with overnight lows between 49° and 54°. The average high for August is 71° with an average low of 51°. AccuWeather's monthly forecast extends further ahead than any other source, with day-by-day RealFeel® Temperatures giving a complete picture of how August weather will actually feel in San Juan Island. See also: September | October | November.
