Iguazu Falls in February

March through May and September through November hit the sweet spot — decent water levels without the crushing summer heat or winter crowds. December through February brings 100°F temperatures and every tour bus in South America. June through August is cooler but drier, so the falls lose some of their punch. The water flow changes dramatically based on rainfall upstream. After heavy rains, the falls turn chocolate brown and roar like freight trains. During dry spells, some of the smaller cascades barely trickle. Check recent photos online before you go — there's nothing worse than showing up to find Devil's Throat at half power. Weekdays are always better than weekends. Get to the parks right when they open at 8 AM to beat the tour groups.