S
M
T
W
T
F
S
27
65°
48°
28
64°
46°
29
63°
53°
30
65°
49°
1
68°
51°
2
71°
52°
3
70°
51°
4
74°
52°
5
70°
54°
6
68°
49°
7
68°
48°
8
70°
49°
9
67°
48°
10
64°
46°
11
62°
48°
12
64°
46°
13
61°
48°
14
60°
47°
15
62°
48°
16
61°
46°
17
58°
41°
18
62°
44°
19
64°
47°
20
63°
47°
21
61°
45°
22
60°
45°
23
62°
49°
24
58°
47°
25
58°
45°
26
59°
43°
27
52°
39°
28
52°
39°
29
51°
41°
30
51°
39°
31
50°
38°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
October Weather in Mercer Island
Mercer Island's October 2026 forecast shows daily high temperatures ranging from 50° to 74°, with overnight lows between 38° and 54°. The average high for October is 61° with an average low of 46°. AccuWeather's monthly forecast extends further ahead than any other source, with day-by-day RealFeel® Temperatures giving a complete picture of how October weather will actually feel in Mercer Island. See also: November | December | January.
