Travelers can visit Ecuador year-round; certain areas are better at certain times of the year, but there are no absolutes. In terms of the weather, El Niño hits hard about one winter every decade, playing havoc with road and rail connections and making communication spotty in some outlying areas. If you're visiting the Galápagos, you'll find the warm rainy season from January to April is the best time for snorkeling; the rest of the year the water is cooler, typically around 20°C (68°F). The mainland coast has similar weather patterns, and its beaches fill up from January to May during coastal Ecuador's school holidays. June through August sees gringo vacationers descend, though the weather's generally gone chilly by then.
      The highlands' dry season (the best time for hiking and climbing) is June to August, which coincides with the wettest months in the Oriente. Trekking in the Oriente is best done in the dry season, from late August through February. As for crowds and costs, the high season both on the mainland and in the Galápagos tends to be mid-December through January and June to August, when most of the vacationing foreign visitors arrive.