S
M
T
W
T
F
S
26
63°
34°
27
64°
36°
28
65°
43°
29
72°
42°
30
74°
42°
1
79°
46°
2
79°
48°
3
78°
47°
4
75°
49°
5
74°
46°
6
73°
44°
7
72°
47°
8
82°
48°
9
75°
50°
10
74°
47°
11
65°
43°
12
67°
44°
13
72°
45°
14
77°
51°
15
79°
52°
16
80°
53°
17
77°
48°
18
77°
52°
19
79°
53°
20
80°
54°
21
79°
54°
22
71°
51°
23
73°
51°
24
77°
54°
25
81°
55°
26
83°
56°
27
83°
56°
28
75°
51°
29
81°
56°
30
82°
56°
31
78°
55°
1
76°
53°
2
81°
57°
3
83°
58°
4
83°
57°
5
77°
57°
6
82°
58°
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 63° to 83°, with overnight lows between 34° and 58°. The average high for May is 76° with an average low of 50°. 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.
