The shoulder seasons of spring (April and May) and fall (September and October) are the best times to visit Pisa, when there are plenty of sunny, warm but not overly hot days and fewer tourists in the street.
Summers in Pisa can be quite hot, with temperatures rising to more than 90 F/32 C in July and August, which makes it tiring for walking and sightseeing. Furthermore, many residents leave the city at this time, so quite a few restaurants and shops may be closed for all or part of the summer, particularly in August.
Winters tend to be cooler, although not freezing, and there can be the odd cold and rainy spell. Visitors will generally need a warm coat and umbrella if visiting Pisa in the winter months.