Since Ecuador lies on the equator its weather is entirely tropical. Within the tropics, seasons are defined on the basis of rainfall rather than temperature variations. In most of Ecuador except for the Galapagos and the dry coastal southwest, the dry season is known as “verano”, the Spanish word for summer. This is because this season is sunnier and somewhat warmer. During the wet season, known as “invierno” the Spanish word for winter, rain falls almost daily and because of this the humidity is quite high. Mornings are usually clear and rainstorms are frequent in the mid to late afternoon. There are no hurricanes or tornados at all and snowstorms in the highest elevations are rare. As in most of the tropics there is more variation between day and nighttime temperatures than there is between seasons. Weather patterns vary greatly depending on geographical regions.
The climate of the coastal region is strongly seasonal with a pronounced hot and rainy season from January to April in most years. In the north, annual rainfall ranges from 1,300 to over 3,000 mm (50 to 120 in). This area receives the influence of the warm California current at it southern limits. As the prevailing winds move the moisture inland, it cools down and precipitates creating a lush, evergreen Tropical rainforest. In the south, the cold Humboldt Current in the ocean just off-shore reaches its northern limits. The cool air passes from the sea over land. As this air warms it expands and sucks moisture out of the atmosphere, producing desert like conditions (the Sechura Desert). This region is dry for all but a short rainy season, usually beginning in March but sometimes extending from January to March. The annual rainfall in the southwest coast ranges from less than 500 to 1,300 mm (20 to 50 in). During the rainy season along the coast the temperature ranges from 22o C. (73o F.) at night to 33o C. (91o F.) during the day with extremely high humidity, most rain falls are relatively brief but strong showers.
Periodically, changes in the oceanic currents in the Pacific lead to a phenomenon known as “El Niño”, “the Christ child”, because it usually starts around Christmas. El Nino conditions bring torrential rains and are caused by unusually high oceanic temperatures in the eastern Pacific. The “El Nino” condition can cause extensive flooding and disruption to services and communication. This event occurs every 5 to 16 years, with the last two major “El Niños” events happening in 1982-1983 and 1998-1999. During these years the dry season lasts from May to December when temperatures are usually a few degrees cooler than in normal years. At this time misty conditions prevail on the Coastal Cordillera for much of the year. In the far northern areas weather pattern does not change much other than being slightly drier, cooler at night and hotter in the middle of the day when compared with the rainy season. In the driest southern coast a mist called “garua” (a constant light drizzle) settles over making the days cloudy and the air being fairly cool and windy. This phenomenon normally appears during the months of June to early August and the temperatures range from 16o C. (60o F.) during the night to 23o C. (73o F.) during the day.
The Ecuadorian Amazon basin or “Oriente” is very warm throughout the year and most precipitation is produced as evaporated water vapor rises above the forest canopy and then cools to fall back down as rainfall. Throughout the region mean annual precipitation exceeds 1,800 mm (70 inches) and may even reach 5,000 mm (197 inches) in the Andean foothills. The rainy season roughly extends from April to mid-December, with June to August usually the wettest months. Temperatures range from 19,5o C. (67o F.) in the night and 36o C. (97o F.) during the day. The driest months are usually December to March where the cumulative rain for the four months average 700 mm (2.3 inches) and the temperature range from 21o C. (70o F.) during the night and 34o C. (93o F.) during the day.
On the Ecuadorian Andes or “La Sierra” the weather pattern is greatly influenced by the weather patterns from lowland areas either to the west or east. The western Andean slopes very much follow the weather pattern dominating on the coastal area and the eastern Andean slopes pretty much follow the weather pattern in the eastern lowlands. The Andean region has higher precipitation levels than the coast and “Oriente”, and there is a higher incidence of mist. The climate of the inter-Andean valleys (since it has a greater influence from the Pacific side or “Costa”) is very seasonal with a drier season from June to September and a short one during the month of December. During the rainy season from October to May, rains can be expected though it does not usually rain daily. In April, the wettest month, it falls on average every other day. Rain frequently falls in the afternoon and evening with mornings generally sunny. Temperature changes little between seasons, but vary greatly each day from 8o C. (46o F.) during the night and 22o C. (72o F.) during the day. Above 3,500 m (11,500 ft) the temperatures regularly reach freezing during the night or when the skies are overcast and the wind blowing. The high elevation grassland (over 3,800m or 12,500 ft) in the Andes is known as “Páramo”. Generally speaking Paramo presents Ecuador’s harshest weather conditions and is the reason why the Ecuadorian “Páramo” has so few people. In Peru and Bolivia this type of region is called “Puna” with a more benign, drier climate allowing greater human population.
One of the many advantages of birding Ecuador is that the special birds can be seen almost year round. The weather you will face depends on the itinerary of your trip and the different geographical areas you will be visiting. For a person who relies strongly on bird vocalizations to locate them, the rainy season is a good choice of time to visit as many birds will be singing at this time and they will be easier to locate. The down side of choosing the rainy season for a birding trip to Ecuador is that you could face a lengthy period of constant rainfall. Such extended wet periods can restrict the quality birding. Visiting any given area during the dry season can also restrict the quality birding to early mornings or late afternoons. I strongly recommend that you time your trip to Ecuador to avoid the rainiest months and the core of the dry season, if at all possible.