There is quite a temperature range between the seasons in the region of Tuscany. During the heat of summer (July and August) you can expect the temperature to rise to an average of 30-35°C (80-90°F) during the afternoon with more mild temperatures 15-20°C (60-75°F) during the spring and fall (April- June; September- November).
The months where you will find the most precipitation and coldest temperatures are December through February (or the very beginning of March). During this time, the locations with the highest altitude are subject to snowfall, and temperatures average around 10°C (40°F) but are known to drop to negative 5-0°C (15-32°F) with occasional snowfall.