S
M
T
W
T
F
S
26
39°
32°
27
43°
30°
28
48°
32°
29
48°
32°
30
48°
30°
1
48°
28°
2
54°
30°
3
55°
34°
4
52°
34°
5
50°
36°
6
41°
22°
7
56°
35°
8
60°
39°
9
61°
38°
10
67°
42°
11
72°
46°
12
75°
48°
13
72°
47°
14
62°
46°
15
69°
45°
16
72°
46°
17
71°
43°
18
69°
44°
19
72°
36°
20
54°
27°
21
56°
28°
22
56°
27°
23
57°
28°
24
57°
27°
25
58°
28°
26
60°
30°
27
66°
35°
28
63°
34°
29
65°
32°
30
67°
33°
31
68°
35°
1
65°
33°
2
64°
34°
3
69°
35°
4
64°
36°
5
62°
36°
6
61°
31°
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 41° to 75°, with overnight lows between 22° and 48°. The average high for May is 63° with an average low of 36°. 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.
