S
M
T
W
T
F
S
26
62°
51°
27
69°
42°
28
63°
43°
29
65°
55°
30
71°
52°
1
68°
41°
2
59°
43°
3
64°
36°
4
78°
41°
5
82°
56°
6
72°
63°
7
65°
48°
8
71°
40°
9
76°
47°
10
85°
54°
11
63°
41°
12
74°
38°
13
79°
52°
14
68°
45°
15
75°
52°
16
85°
59°
17
92°
63°
18
90°
64°
19
89°
66°
20
83°
61°
21
73°
60°
22
78°
59°
23
75°
57°
24
75°
55°
25
76°
57°
26
77°
56°
27
81°
61°
28
80°
62°
29
82°
62°
30
82°
61°
31
79°
60°
1
75°
58°
2
76°
59°
3
76°
58°
4
77°
57°
5
80°
63°
6
84°
64°
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 68° to 92°, with overnight lows between 45° and 66°. The average high for May is 79° with an average low of 59°. 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.
