S
M
T
W
T
F
S
26
63°
44°
27
75°
35°
28
72°
51°
29
65°
49°
30
52°
35°
1
57°
32°
2
48°
31°
3
60°
31°
4
73°
48°
5
74°
58°
6
57°
48°
7
60°
35°
8
63°
35°
9
67°
49°
10
63°
43°
11
63°
37°
12
69°
37°
13
66°
48°
14
54°
43°
15
67°
38°
16
74°
44°
17
83°
53°
18
88°
60°
19
86°
66°
20
75°
51°
21
64°
49°
22
65°
52°
23
70°
52°
24
75°
55°
25
78°
58°
26
79°
65°
27
77°
56°
28
76°
48°
29
75°
49°
30
69°
47°
31
70°
46°
1
73°
52°
2
71°
53°
3
73°
55°
4
77°
56°
5
76°
59°
6
78°
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 69° to 79°, with overnight lows between 46° and 65°. The average high for May is 75° with an average low of 54°. 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.
