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The weather in Siena in August is hot. The average temperatures are between 17°C and 31°C. Usually the days in August are hot while the nights are a bit cooler.
You can expect about 3 to 8 days of rain in Siena during the month of August. It’s a good idea to bring along your umbrella so that you don’t get caught in poor weather.
Our weather forecast can give you a great sense of what weather to expect in Siena in August 2025.
If you’re planning to visit Siena in the near future, we highly recommend that you review the 14 day weather forecast for Siena before you arrive.
| Month | Temperatures | Rainy Days | Dry Days | Snowy Days | Rainfall | Weather | More details |
|---|---|---|---|---|---|---|---|
| January | 9° / 2° | 5 | 25 | 1 | 74 mm | Ok | Siena in January |
| February | 10° / 2° | 5 | 21 | 2 | 85 mm | Bad | Siena in February |
| March | 14° / 4° | 5 | 25 | 1 | 73 mm | Good | Siena in March |
| April | 18° / 7° | 5 | 25 | 0 | 64 mm | Good | Siena in April |
| May | 21° / 9° | 6 | 25 | 0 | 91 mm | Good | Siena in May |
| June | 27° / 14° | 6 | 24 | 0 | 70 mm | Perfect | Siena in June |
| July | 30° / 16° | 3 | 28 | 0 | 42 mm | Good | Siena in July |
| August | 31° / 17° | 3 | 28 | 0 | 38 mm | Good | Siena in August |
| September | 26° / 14° | 4 | 26 | 0 | 81 mm | Perfect | Siena in September |
| October | 20° / 10° | 4 | 27 | 0 | 79 mm | Good | Siena in October |
| November | 14° / 7° | 6 | 24 | 0 | 105 mm | Good | Siena in November |
| December | 10° / 3° | 5 | 25 | 1 | 74 mm | Ok | Siena in December |