WEATHER in SIENA
To talk of the 'weather in Tuscany' is to generalise somewhat. Tuscany encompasses many diverse terrains and landscapes and the rules change from one zone to the next. You can be sure that July and August in Tuscany will be hot, sometimes stiflingly so, thanks to the humidity levels that can make Florence and the major cities of Tuscany veritable hothouses.
This situation is supposed to break around the day of feragosto in the middle of August, when the first rains are expected and with them a beginning of a decrease in temperature. September can still be very hot with October being a fine month to visit Tuscany - blue skies without the packed cities and the intense heat. But, some like it hot! November sees night-time temperatures really begin to drop, with crisp Autumn days to accompany the main olive harvest throughout Tuscany. Winter in Tuscany can be cold and wet but spring always seems to come quickly. March is azalea and camelia time, whilst April and May are sometimes very wet months.
Here you can find some information
about the weather in Siena (always update).