S
M
T
W
T
F
S
26
70°
49°
27
69°
47°
28
69°
48°
29
70°
47°
30
70°
48°
1
71°
48°
2
75°
51°
3
76°
52°
4
71°
49°
5
72°
49°
6
71°
50°
7
72°
49°
8
72°
49°
9
73°
50°
10
76°
51°
11
76°
52°
12
77°
51°
13
74°
50°
14
72°
50°
15
73°
51°
16
76°
51°
17
81°
56°
18
82°
58°
19
82°
58°
20
81°
57°
21
81°
58°
22
79°
57°
23
82°
56°
24
83°
55°
25
80°
57°
26
84°
58°
27
85°
57°
28
86°
56°
29
85°
56°
30
85°
56°
31
84°
56°
1
84°
57°
2
85°
55°
3
85°
55°
4
80°
52°
5
78°
51°
6
78°
54°
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 86°, with overnight lows between 47° and 58°. The average high for May is 78° with an average low of 53°. 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.
