Check How Hot & Sunny It Is Before You Book Your Next Holiday in 2020 to Florence, Tuscany September weather forecast for Florence, Italy. The weather in Florence in the month of september comes from statistical datas on the last years. Get the monthly weather forecast for Florence, Tuscany, Italy, including daily high/low, historical averages, to help you plan ahead. Florence Weather in September - Temperature, Rainfall & Sunshine. Autumn begins in September with a reduction in the average temperatures to the range of 18°C (64.4°F) and 27°C (80.6°F) taking away the scorch of summer. You can view the weather statistics for the whole month, but also by using the tabs for the beginning, the middle and the end of the month. Weather in Florence in september 2020. Weather reports from September 2017 in Firenze, Italy with highs and lows