S
M
T
W
T
F
S
26
60°
43°
27
73°
42°
28
69°
51°
29
54°
45°
30
54°
40°
1
45°
36°
2
42°
33°
3
59°
46°
4
70°
58°
5
66°
45°
6
54°
38°
7
53°
38°
8
57°
42°
9
62°
46°
10
61°
47°
11
60°
44°
12
61°
46°
13
64°
51°
14
64°
49°
15
66°
48°
16
65°
62°
17
75°
56°
18
73°
55°
19
71°
55°
20
75°
54°
21
73°
51°
22
67°
46°
23
65°
47°
24
66°
47°
25
66°
50°
26
67°
49°
27
67°
48°
28
68°
49°
29
68°
49°
30
69°
53°
31
74°
56°
1
70°
53°
2
71°
54°
3
74°
59°
4
75°
58°
5
76°
60°
6
80°
61°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
May Weather in Ontario
Ontario's May 2026 forecast shows daily high temperatures ranging from 53° to 80°, with overnight lows between 38° and 62°. The average high for May is 67° 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 May weather will actually feel in Ontario. See also: June | July | August.
