Siena weather in May
May in Siena: nice, rainy, with clean air — an excellent time to visit.
#3 of 12 months in Siena · #220 of 897 destinations to visit in May · comfort 89/100 (tier A)
Updated June 2026 · climate normals from ERA5 reanalysis
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Siena climate normals — May
| Daytime high | 21°C / 69°F | 😎 nice |
|---|---|---|
| Nighttime low | 10°C / 51°F | |
| Rainfall | 84 mm / 3.3 in | 🌧 rainy |
| Rainy days | 13 days | |
| Humidity | 74% | 💧 humid |
| Dew point | 12°C / 53°F | |
| Sunshine | 11.3 h/day | |
| Daylight | 14.7 h | |
| Wind | 15 km/h / 9 mph | |
| Air quality (US AQI) | 44 | 🍃 good |
Monthly averages from ERA5 reanalysis. AQI is the mean US Air Quality Index for the month.
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Siena in May — FAQ
- Is May a good time to visit Siena?
- May in Siena: nice, rainy, with clean air — an excellent time to visit. It ranks #3 of 12 months for Siena on SeasonMap's comfort score (89/100).
- What is the weather like in Siena in May?
- In May, Siena averages a daily high of 20.5°C and a low of 10.3°C, with about 83.7 mm of rain over roughly 13.2 rainy days.
- What is the air quality in Siena in May?
- Siena has a mean US Air Quality Index of about 44 in May.