Weather
Being a tropical country not very far north of the equator, Panama has two distinct seasons: the dry season and the wet, or rainy, season. The latter starts in late April, so by May, visitors to Panama should expect some rain every day. However, it doesn't generally rain all day every day. Instead, there's usually a thunderstorm or heavy rain shower for some time in the afternoon, which cools the air somewhat. The Pacific coast and Caribbean coast experience slightly different climates, with the Caribbean coast being wetter year-round.
As for temperatures, the annual average temperature in Panama is 86°F (30°C). This rises a bit in the dry season but is slightly cooler in the rainy season, and is always a bit cooler in the higher-altitude highlands. However, the humidity is higher in the rainy season, which many people find more uncomfortable than hot and dry conditions.
Crowds & Costs
The whole rainy season is low tourism season in Panama, so this is actually a good time to come if you're on a tight budget and need to cut costs where possible. As long as you expect to get wet and realize that some activities (like lying on a beach or hiking through a rainforest) won't be much fun in May, this can be a good time to come to avoid the crowds and high prices.
Where to Go
Although wildlife lovers will need to give the rainforests a wide berth in the rainy season, there's another reason to be excited: loggerhead and green sea turtles begin nesting in May. This nesting continues through the rainy season. Visit Bocas del Toro, on the Caribbean coast, or Isla Cañas (Cane Island), south-east of Panama City, to see this wonder of nature.
Chat with a local specialist who can help organize your trip.
What to Do
General sightseeing in Panama's beautiful and historic towns and cities is a good activity to enjoy when the weather's wet. Panama City is home to great museums, restaurants, and historic enclaves that are ideal in both wet and dry weather. You can also tour the Miraflores Locks at the Panama Canal in any season. Other towns and cities worth visiting for some sightseeing include David, Colon, and Las Tablas. Just take an umbrella.
If you're into adventure sports, white-water rafting can be fun in May, with rivers swollen from rain. In fact, the rainy season is the best time to raft as most rivers are unnavigable in the dry season. Chiriqui has some of the best rafting in Panama. Scuba-diving is also possible in the rainy season (and you'll be getting wet anyway, right?).
Events in May
Fiesta de Corpus Christi. Held 60 days after Good Friday, this religious festival is a colorful display of local culture in Panama. Chitre and Los Santos are especially good places to be during this festival. "Clean" and "dirty" devils dance through the streets, wearing horns and fascinating masks. This festival can also be in June, depending on the timing of Easter.
Traveling to Panama in May? Check out these great itineraries
Panama History & Nature Tour - 8 Days. Harken back to the days when Panama was rich with colonial ports and pirate invasions on this itinerary that combines nature and culture.
Best of Panama City - 7 Days. Melding colonial history and bold modernity, the cosmopolitan capital of Panama is a thriving hub in Central America.
The Wonders of Panamá - 7 Days. Panama is a beautiful country brimming with history and diversity, and this week-long itinerary offers an exciting sampling of its many charms.