S
M
T
W
T
F
S
26
35°
20°
27
37°
19°
28
30°
18°
29
28°
21°
30
27°
19°
1
32°
18°
2
57°
31°
3
55°
32°
4
53°
30°
5
47°
24°
6
37°
21°
7
52°
33°
8
56°
35°
9
58°
36°
10
54°
33°
11
57°
38°
12
59°
36°
13
58°
38°
14
59°
37°
15
55°
26°
16
58°
31°
17
55°
29°
18
59°
32°
19
53°
24°
20
56°
27°
21
53°
24°
22
56°
31°
23
60°
31°
24
51°
29°
25
51°
25°
26
53°
27°
27
55°
32°
28
52°
31°
29
53°
33°
30
54°
31°
31
53°
32°
1
55°
30°
2
57°
31°
3
60°
31°
4
58°
32°
5
56°
32°
6
59°
34°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
May Weather in Keystone
Keystone's May 2026 forecast shows daily high temperatures ranging from 37° to 60°, with overnight lows between 21° and 38°. The average high for May is 55° with an average low of 31°. AccuWeather's monthly forecast extends further ahead than any other source, with day-by-day RealFeel® Temperatures giving a complete picture of how May weather will actually feel in Keystone. See also: June | July | August.
