Colonia del Sacramento in December

March through May gives you the best weather without the crowds. Temperatures hover around 70°F, perfect for walking those cobblestones without sweating through your shirt. The autumn light makes the colonial buildings look even more photogenic. Summer (December through February) brings heat and humidity plus crowds of Argentine tourists escaping Buenos Aires. Hotels fill up and prices spike. But the longer days mean you can catch sunset from the lighthouse around 8 PM. Winter isn't terrible if you don't mind cooler weather. June and July see temperatures around 50°F, which is fine for exploring during the day. Just pack layers because the wind off the river cuts right through you. Avoid visiting during Carnival in February unless you're specifically here for the festivities. The town transforms but accommodation becomes nearly impossible to find.