Siena weather in December
December in Siena: cool, rainy, with clean air — a good time to visit.
#12 of 12 months in Siena · #598 of 897 destinations to visit in December · comfort 63/100 (tier C)
Updated June 2026 · climate normals from ERA5 reanalysis
Traveller notes on Siena in December
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Siena climate normals — December
| Daytime high | 11°C / 51°F | 🙂 cool |
|---|---|---|
| Nighttime low | 3°C / 38°F | |
| Rainfall | 115 mm / 4.5 in | 🌧 rainy |
| Rainy days | 12 days | |
| Humidity | 89% | 💦 very humid |
| Dew point | 6°C / 43°F | |
| Sunshine | 5.3 h/day | |
| Daylight | 9 h | |
| Wind | 13 km/h / 8 mph | |
| Air quality (US AQI) | 37 | 🍃 good |
Monthly averages from ERA5 reanalysis. AQI is the mean US Air Quality Index for the month.
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Siena in December — FAQ
- Is December a good time to visit Siena?
- December in Siena: cool, rainy, with clean air — a good time to visit. It ranks #12 of 12 months for Siena on SeasonMap's comfort score (63/100).
- What is the weather like in Siena in December?
- In December, Siena averages a daily high of 10.8°C and a low of 3.2°C, with about 115.3 mm of rain over roughly 12.4 rainy days.
- What is the air quality in Siena in December?
- Siena has a mean US Air Quality Index of about 37 in December.