Ecuador is divided into three distinctive climatic zones (four, if you count the coast and Galápagos as separate).
Quito & Highlands: Quito is broadly representative of the climate in the Highlands region, and is experiencing its soggiest month of the year this month. Still, there are periods of sunshine nevertheless (usually in the morning) and the good news is that drier weather is just around the corner!
Oriente/Amazon: Ecuador's Amazon climate varies because this is a vast region. In Parque Nacional Yasuni, probably the most relevant destination for travelers, average rainfall keeps dramatically increasing: 10.5 inches/268mm for this month.
Desert Coastal Strip & Galapagos: On the coast, it is still high season in April because of the continued high temperatures: Guayaquil is experiencing its second-hottest month now with temperatures at over 80°F/26.9°C. On the Galapagos, it's still warm but much less wet, with the islands under a sea of lush colors brought on by the combination of sun and rain.
Crowds & Costs
If Easter should fall in April, be prepared for price hikes and dramatically increased crowds. Both Ecuadorians and foreign travelers take holidays at this time. Other than that, it's the last month of high season on the coast and still low season in the Highlands and in the Oriente/Amazon.
Where to Go
Quito & Highlands: Quito is among the rainiest places in Ecuador at the moment and this is the rainiest month of the year. Hole up in one of Quito's incredible restaurants, explore its colonial churches or its seminal museums like the New Town's Museo Nacional. Views of the cloud-laced mountains are still spectacular here. And still make the trip to Otavalo, where the famous artisan market has its stalls under shelter, meaning you can still browse happily. In Mindo, April is the last month of the truly spectacular birding season.
Oriente/Amazon: Increased rainfall makes it a particularly good time to visit the Cuyabeno Reserve, where small creeks are filling with water again, making for the best chances for wildlife observation on canoe rides there. Or take the Ruta de las Cascadas drive from Baños (officially in the Highlands but on the cusp of the jungle) down to Puyo: waterfalls are in spate right now.
Desert Coastal Strip & Galapagos: This is one of the best months for visiting the Galapagos (along with next month) because of the warm weather, animal activity and the fact the rain (now slackening off a little) has made the landscapes particularly lush.
What to Do
Quito & Highlands: It could be time, given the wet weather, to browse one of the Highlands' fantastic museums, or one of its colonial churches (Quito and Cuenca have the greatest selection), try the sensational mix of gourmet and traditional food in Quito or Cuenca or browse the famous traditional markets at Otavalo.
Oriente/Amazon: Here, it's time to take a canoe trip into some of the Amazon's smaller tributaries for unparalleled wildlife watching. White-water rafting remains a good bet on Amazonian rivers this month because of the high water levels.
Desert Coastal Strip & Galapagos: Have a go at snorkeling, especially good in the warm and clear waters of the Galapagos. And make the most of the warm weather with some time sun-bathing on the beaches: it's the end of high season and optimum beach weather here.
Semana Santa (Holy Week): Religious processions fill the streets of main towns and cities with a beautiful solemnity in this week leading up to Easter in April, should Easter fall after the beginning of April.
Founding Day: April 12. People in Cuenca celebrate the founding of their city with traditional food, parades and Carnaval-style floats.
Fiesta de Chonta: Mid-April. In the Amazonian town of Archidona, this celebrates the importance of the chonta fruit to the local economy and culture. A special fermented beverage made from the chonta is drunk in ample quantities.
Independence Battle of Tapi: April 21. This event celebrates the battle that gave the Highland city of Riobamba its independence. It's a good festival for observing local customs and is based around an agricultural fair. Traditional food is served and there is lots of singing and dancing.