S
M
T
W
T
F
S
26
60°
53°
27
64°
49°
28
69°
48°
29
72°
51°
30
74°
51°
1
68°
52°
2
63°
52°
3
64°
53°
4
62°
50°
5
62°
52°
6
68°
55°
7
70°
53°
8
67°
52°
9
69°
53°
10
70°
53°
11
80°
53°
12
68°
52°
13
69°
55°
14
78°
54°
15
77°
54°
16
72°
54°
17
74°
51°
18
82°
64°
19
86°
58°
20
84°
57°
21
85°
55°
22
76°
54°
23
70°
54°
24
69°
54°
25
70°
52°
26
78°
55°
27
86°
52°
28
81°
50°
29
81°
49°
30
86°
48°
31
86°
49°
1
86°
48°
2
87°
51°
3
85°
51°
4
82°
49°
5
77°
50°
6
79°
49°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
May Weather in Port Costa
Port Costa's May 2026 forecast shows daily high temperatures ranging from 69° to 87°, with overnight lows between 48° and 55°. The average high for May is 80° with an average low of 51°. 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 Port Costa. See also: June | July | August.
