S
M
T
W
T
F
S
26
65°
51°
27
65°
50°
28
73°
46°
29
76°
49°
30
75°
52°
1
78°
56°
2
78°
54°
3
67°
54°
4
65°
52°
5
64°
53°
6
76°
48°
7
80°
53°
8
78°
56°
9
83°
57°
10
84°
56°
11
90°
57°
12
71°
56°
13
75°
56°
14
74°
53°
15
71°
56°
16
70°
58°
17
66°
57°
18
80°
56°
19
87°
51°
20
88°
58°
21
83°
57°
22
77°
56°
23
78°
56°
24
76°
56°
25
75°
56°
26
73°
55°
27
71°
56°
28
72°
55°
29
80°
54°
30
76°
56°
31
85°
57°
1
84°
58°
2
83°
59°
3
82°
58°
4
81°
59°
5
80°
58°
6
82°
57°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
May Weather in Diamond Bar
Diamond Bar's May 2026 forecast shows daily high temperatures ranging from 71° to 85°, with overnight lows between 54° and 59°. The average high for May is 79° with an average low of 57°. 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 Diamond Bar. See also: June | July | August.
