Weather
A reminder to travelers from the northern hemisphere: the seasons are opposite in the southern hemisphere, meaning that May is the middle of autumn in Argentina and Brazil. But don't expect crisp weather and trees changing color—this region, covered with jungle, stays warm and humid throughout the year. Autumn is certainly a more comfortable time to visit than summer, however: expect highs in the low- to mid-80s and lows in the upper 60s.
May falls squarely in the region's dry season, too: expect blue skies. It's possible, but not particularly likely, to encounter a rainy day during a short stay at Iguazú. The level of the river is lower than in summer, thanks to less rainfall; catwalks in the park stay dry, making hiking easier and safer, even if the views of the waterfalls are slightly less dramatic.
Crowds & Costs
Expect lots of international visitors at Iguazú in May: it's a popular travel time, though not nearly as busy as in summer, when Brazilians and Argentines are on vacation and the region sees a major uptick in domestic travel. Hotel rates are stable at this time of year. But especially on weekends, hotels fill up and car rental companies may start running out of vehicles to rent.
It's wise to book ahead of time if you're planning to drive—or if you have your heart set on a particular hotel. During the week, you'll enjoy relative peace and quiet in the parks, especially if you get an early start in the morning and beat the tourist crowds.
What To Do
Make a beeline to Garganta del Diablo (Devil's Throat), the lookout point over one of the waterfalls' most dramatic sections, first thing in the morning. Accessible by hiking trail and train, this key attraction takes a while to get to, and if you do it right when the park opens, you'll practically have the place to yourself. Photographers may opt to see Garganta del Diablo later in the afternoon when the sun is positioned behind the platform instead of behind the falls: this is the best time to take photos.
Enjoy hiking in the park at this time of year: it's not too hot in May, and wildlife, from birds to butterflies, are especially active in autumn. The temperatures are still hot enough that you won't mind getting wet—and you will get drenched, indeed, on the Gran Aventura excursion that takes visitors to the base of the falls in an all-terrain vehicle and speedboat.
Because the river level is relatively low at this time of year, boat rides depart regularly (they're often postponed or even canceled when the river is running high in summer). If you'd rather stay dry, opt for the calmer Ecological Trip, a rafting ride that leaves from the Garganta del Diablo train station. Check online or inquire at the Visitors Center for more information.
Chat with a local specialist who can help organize your trip.
What To Look For
Autumn is an ideal time of the year for wildlife spotting. The area around Iguazú Falls is home to 430 species of birds, including toucans, hummingbirds, and brightly plumed plush-crested jays, plus 70 species of mammals, from playful capuchin monkeys to raccoon-like coatis (they're cute at first, but they'll steal food right out of your hand if you give them a chance, which is why the parks have protected areas for eating). Vibrantly hued butterflies flutter around hikers on the parks' trails, too—don't be surprised if a butterfly rides along on your arm or backpack as you make your way along the catwalks.
Fall is a good time for key photo ops at attractions like Garganta del Diablo and Bossetti Jump. Time things right and you'll be able to take pictures without tourists around: it's best to get into the park early, or to stay late, when tourists start heading out, to optimize your chances.
Events & Activities
Walks in the Moonlight: Iguazú National Park offers guided nocturnal tours on five evenings each month. The schedule depends on the lunar calendar. Sign up ahead of time for the chance to see the park’s natural attractions under the moonlight, plus owls and other creatures that only come out at night. Several departures are available (7:45, 8:30, and 9:15 pm) and reservations are required.
Visiting Iguazú Falls in May? Check out these itineraries.
Buenos Aires & Iguazú Falls Experience - 7 Days Begin your journey in Buenos Aires and head to Iguazú Falls to see the jaw-dropping beauty of the largest waterfall system in the world. You'll get to experience the falls from both Argentina and Brazil, and take in a tango show in the capital city.
Ultimate Iguazú Falls Experience - 4 Days This four-day getaway to Iguazú Falls takes you into the heart of one of Argentina’s most prized destinations. Then, you'll experience another side of the falls from Brazil, with expansive, panoramic views.
More Helpful Information
Ultimate Guide to Iguazú National Park
Argentina in May
Argentina Tours & Itineraries
Iguazú Falls in April
Iguazú Falls in June