S
M
T
W
T
F
S
26
66°
33°
27
59°
38°
28
54°
46°
29
73°
42°
30
79°
41°
1
78°
42°
2
82°
51°
3
90°
48°
4
81°
46°
5
73°
46°
6
69°
53°
7
71°
47°
8
64°
44°
9
79°
47°
10
67°
46°
11
82°
48°
12
89°
49°
13
57°
46°
14
58°
46°
15
49°
42°
16
48°
40°
17
57°
40°
18
68°
39°
19
64°
44°
20
70°
50°
21
81°
44°
22
81°
47°
23
72°
47°
24
76°
46°
25
66°
47°
26
62°
46°
27
78°
47°
28
83°
51°
29
59°
48°
30
63°
44°
31
71°
42°
1
82°
41°
2
87°
48°
3
72°
55°
4
69°
52°
5
59°
48°
6
29°
18°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
May Weather in Mount Saint Helens National Volcanic Monument
Mount Saint Helens National Volcanic Monument's May 2026 forecast shows daily high temperatures ranging from 29° to 29°, with overnight lows between 18° and 18°. The average high for May is 29° with an average low of 18°. 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 Mount Saint Helens National Volcanic Monument. See also: June | July | August.
