S
M
T
W
T
F
S
26
64°
50°
27
64°
51°
28
72°
47°
29
74°
50°
30
74°
53°
1
77°
55°
2
77°
55°
3
65°
54°
4
64°
52°
5
62°
52°
6
74°
49°
7
80°
54°
8
78°
55°
9
82°
55°
10
83°
55°
11
90°
58°
12
70°
56°
13
74°
57°
14
73°
54°
15
71°
56°
16
70°
57°
17
65°
56°
18
79°
56°
19
86°
53°
20
86°
60°
21
82°
58°
22
76°
56°
23
76°
56°
24
N/A
25
75°
56°
26
72°
56°
27
68°
54°
28
69°
55°
29
77°
54°
30
77°
56°
31
86°
57°
1
85°
59°
2
84°
59°
3
82°
58°
4
84°
59°
5
82°
58°
6
79°
57°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
*Temporarily Unavailable
May Weather in Ontario
Ontario's May 2026 forecast shows daily high temperatures ranging from 68° to 86°, with overnight lows between 54° and 59°. The average high for May is 78° with an average low of 57°. 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.
