S
M
T
W
T
F
S
26
62°
44°
27
64°
45°
28
66°
50°
29
67°
50°
30
68°
51°
1
68°
51°
2
67°
52°
3
68°
52°
4
67°
53°
5
68°
52°
6
65°
49°
7
67°
52°
8
70°
54°
9
71°
53°
10
71°
54°
11
72°
54°
12
70°
53°
13
72°
55°
14
68°
55°
15
67°
54°
16
68°
53°
17
67°
52°
18
67°
52°
19
68°
53°
20
67°
54°
21
69°
51°
22
74°
58°
23
75°
57°
24
72°
53°
25
71°
57°
26
72°
57°
27
72°
56°
28
74°
58°
29
75°
56°
30
76°
57°
31
77°
60°
1
78°
60°
2
78°
56°
3
73°
54°
4
74°
58°
5
75°
55°
6
74°
58°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
May Weather in Siena
Siena's May 2026 forecast shows daily high temperatures ranging from 62° to 78°, with overnight lows between 44° and 60°. The average high for May is 70° with an average low of 54°. 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 Siena. See also: June | July | August.
