Ecuador has two seasons: wet and dry, which have much to do with the part of the country you are in. Generally speaking, the temperature is dictated by altitude. Quito and the Andes enjoy spring-like weather year-round, with highs of around 20-25° C (68-77°F) and lows of about 8-10°C (45-50°F). Weather in the Galapágos varies between misty and cool, and steamy and sunny. The Amazon region is generally either hot and humid, or hot and rainy.
The wet season or invierno (winter) in the highlands is from October until April (with a short dry period from mid-November to the end of December), and the dry season, verano (summer) lasts from June until September. However, no matter what season it is said to be, the weather is ultimately unpredictable. Warm sunny mornings can often lead to bone-chilling, rainy afternoons, hence the sierra’s adage “four seasons in one day.”
The Pacific Coast is at its coolest from June to November, when it is often cloaked in garúa, a thick, foggy mist. Generally, the region is warm and humid year round, with temperatures averaging 25 degrees C (76 F) to 31 C (90 F). The rainy season- from December to May- is warm and muggy. The dry season is less humid, but by no means dry. It tends to be wettest in the north (Esmeraldas) and driest in the South near the Peruvian border. Temperatures in the Oriente hover around the high 20s to low 30s (high 80s to 90s°F). It rains most days in this area, but the wettest months are April to September. Some secondary roads may be closed due to flooding at this time, which can put off a trip if it involves road travel off the main roads. Many of the lodges in the Oriente are reached by canoe. During the dry months, especially December to February, many of the subsidiary rivers completely dry up and lodges are reached by foot instead of canoe. This provides a completely different experience and you may want to check with your tour operator before lugging your bags along the dried-up river bottom.
In the Galapagos there is a rainy season, a dry season and a transition season. The months of June to December tend to be characterized by cool garúa (mist) and temperatures averaging 72 F. From January to May, the climate is more typically tropical: hot air temperatures, wide stretches of blue sky, and occasional brief downpours. Because many of the islands are covered in black (bare) lava rock, you may feel yourself baking (and burning) in the heat.