October is one of the wettest two months of the year in Tuscany. Florence has an average of 89mm rainfall during the month. Pisa averages 119mm. (For comparison, London has an average of just 74mm). At the start of the month, average maximum temperatures are around 23C (falling to 12C overnight). By the end of the month, the average maximum temperature is around 18C (falling to around 7C overnight).
Detailed information for Pisa is here:
http://uk.weather.com/weather/climatology/ITXX 0059?dayofyear=274
Here's the eqivalent data for Florence:
http://uk.weather.com/weather/climatology/ITXX 0028?dayofyear=274
Chris