Florence is a year-round gallery city. The constraint is heat and tickets, not closed monuments.
April–June and September–October
Walking weather, Chianti harvest in autumn, and peak ticket competition. Book Uffizi and Accademia first.
July–August
Hot. Start at opening. Many Florentines leave in August. The stones hold heat; the dome climb is harder.
November–March
Quieter galleries, lower rates, grey light. A good city-break window if you came for art, not hills.