S
M
T
W
T
F
S
26
57°
40°
27
51°
37°
28
54°
39°
29
53°
35°
30
53°
33°
1
55°
32°
2
52°
32°
3
53°
36°
4
52°
35°
5
54°
35°
6
55°
37°
7
55°
37°
8
57°
38°
9
58°
37°
10
57°
39°
11
57°
37°
12
58°
40°
13
63°
40°
14
58°
41°
15
58°
42°
16
60°
43°
17
60°
41°
18
61°
40°
19
63°
51°
20
72°
51°
21
73°
46°
22
63°
42°
23
64°
43°
24
64°
44°
25
70°
50°
26
74°
53°
27
75°
48°
28
70°
45°
29
71°
47°
30
73°
51°
31
67°
54°
1
72°
46°
2
67°
45°
3
67°
44°
4
65°
50°
5
68°
53°
6
69°
53°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
May Weather in Ottawa South
Ottawa South's May 2026 forecast shows daily high temperatures ranging from 51° to 75°, with overnight lows between 32° and 54°. The average high for May is 62° with an average low of 42°. 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 Ottawa South. See also: June | July | August.
