July brings 31°C daytime highs, 22mm of precipitation across about 3 wet days and 14.9 hours of daylight — best for beach days, swimming and reliable sunshine. The strongest run of the year is June to August. December is the quietest month: quiet and local, and still good for festive season, low-angle light and quiet and local.
Long-run climate normals for Siena. Month ratings compare months within Siena only — they are not a ranking of Siena against other destinations, and they are not a forecast for a specific year.
Last updated: · Live forecast data refreshes hourly.
| Best month | July — Beach days, Swimming, Reliable sunshine |
| Best 3-month window | June–August |
| Quietest month | December — Quiet and local |
| Driest month | July — 22mm |
| Wettest month | November — 82mm |
| Warmest / coolest | July 31°C / February 8°C |
| Seasonality | Fairly even across the year |
| Annual rainfall | 760mm over roughly 78 rain days |
December gets roughly 182% more precipitation than July — 62mm against 22mm. That difference, more than temperature, is what changes how a day here feels.
Siena swings 23°C between July (31°C) and February (8°C) — the month you pick changes what you pack more than where you go.
June gives you 15.2 hours of daylight against just 8.8 in December — a 6-hour difference in how much you can actually fit into a day.
July is the driest month at 22mm across roughly 3 wet days, while November peaks at 82mm.
August is almost as good as July, but usually quieter and cheaper. If your dates are flexible, it is the easier trip.
Siena stays fairly consistent all year, so there is no month you need to avoid. What you plan to do matters more than when you go.
Ratings compare months within Siena, not against destinations worldwide: five stars means the best time to be here, not that Siena beats anywhere else. Tags describe what the conditions actually suit.
| Month | Rating | High / Low | Precipitation | Wet days | Sun | Daylight | Best for |
|---|---|---|---|---|---|---|---|
| January | ★★☆☆☆ | 8°C / 1°C | 48mm | 6 | 5h | 9.1h | Low-angle light · Quiet and local |
| February | ★★☆☆☆ | 8°C / 1°C | 42mm | 5 | 5h | 10.3h | Low-angle light · Quiet and local |
| March | ★★☆☆☆ | 11°C / 3°C | 52mm | 7 | 5h | 11.7h | Spring greenery · Quiet and local |
| April | ★★★★☆ | 17°C / 7°C | 58mm | 7 | 4h | 13.3h | Hiking · Cycling · Spring greenery |
| May | ★★★★★ | 22°C / 12°C | 56mm | 7 | 6h | 14.6h | Hiking · Cycling |
| June | ★★★★★ | 28°C / 16°C | 38mm | 5 | 7h | 15.2h | Beach days · Swimming |
| July | ★★★★★ | 31°C / 18°C | 22mm | 3 | 11h | 14.9h | Beach days · Swimming · Reliable sunshine |
| August | ★★★★★ | 31°C / 18°C | 28mm | 4 | 11h | 13.7h | Beach days · Swimming · Reliable sunshine |
| September | ★★★★★ | 28°C / 16°C | 55mm | 7 | 11h | 12.3h | Beach days · Swimming · Reliable sunshine |
| October | ★★★★☆ | 22°C / 12°C | 72mm | 9 | 6h | 10.7h | Hiking · Cycling · Low-angle light |
| November | ★★☆☆☆ | 17°C / 7°C | 82mm | 10 | 4h | 9.5h | Hiking · Cycling · Autumn colour |
| December | ★★☆☆☆ | 11°C / 3°C | 62mm | 8 | 3h | 8.8h | Festive season · Low-angle light · Quiet and local |
| You are planning | Pick | Why |
|---|---|---|
| Sun & beach days | July | 11h daily sunshine, 31°C highs and only 3 rain days. |
| City walking & sightseeing | May | 22°C highs with 14.6h of daylight — long days without heat fatigue. |
| Photography & light | July | 11h of sun and 14.9h daylight give the widest window for golden-hour work. |
| Value & fewer crowds | June | Scores 78/100 — close to peak conditions but outside the busiest window. |
| Cooler-weather travel | April | 17°C highs and 7°C nights suit anyone who dislikes heat. |
Each month in Siena is described from long-run climate normals and then rated relative to the other eleven months in the same city. A five-star January in a cold destination means January is one of the best times to be there — not that it beats a Mediterranean summer.
| Factor | Weight | What it measures |
|---|---|---|
| Temperature | Described | Average daytime high and overnight low for the month, shown as measured rather than judged. |
| Precipitation | Described | Monthly millimetres and wet-day count, labelled as snow or rain/snow where temperatures make that the likely phase. |
| Sunshine & daylight | Described | Average daily sunshine hours and astronomical daylight length at mid-month, from the city’s latitude. |
| “Best for” tags | Derived | Applied only when the conditions genuinely support the activity — snow depth-friendly cold for skiing, 13–24°C and low rain risk for hiking, dark evenings at high latitude for aurora. A month with few strong use cases gets fewer tags rather than padded ones. |
| Star rating | Relative | Ranks the month against the other eleven months in the same city. Never a comparison between cities. |
Figures are long-run climate averages, not a forecast for a specific year. Where a month lacks sourced rainfall or humidity, the value is modelled from temperature range and rain frequency.
July is the best all-round month in Siena: 31°C highs, 22mm of precipitation and 14.9 hours of daylight, which suits beach days, swimming and reliable sunshine. The strongest three-month window is June to August.
December — 11°C highs, 62mm of precipitation over roughly 8 days and 8.8 hours of daylight. It is the cheapest and least crowded time to go, and it still works for festive season, low-angle light and quiet and local.
July is the driest month at 22mm over about 3 rain days, against 82mm in November. Across the year Siena records around 760mm.
Yes — conditions in Siena stay fairly even all year, so there is no month you need to avoid. What you plan to do matters more than when you go.
Daylight ranges from 8.8 hours in December to 15.2 hours in June, calculated from the city's latitude.