The Galápagos Islands are an archipelago situated directly on the equator, approximately 900 kilometers west of Ecuador’s mainland. While this location suggests a perpetually hot, humid, and rainy tropical climate, the reality is far more complex. The islands’ environment is defined by a highly variable climate profile, an anomaly for an equatorial zone. This unexpected weather results from the interplay between powerful ocean currents, trade winds, and the volcanic topography. The archipelago experiences distinct seasonal shifts and microclimates that shape its world-renowned biodiversity.
Equatorial Location and General Conditions
The islands straddle the equator, ensuring consistent solar radiation and near-uniform daylight hours throughout the year. Despite this intense solar exposure, the overall climate is classified as subtropical and semi-arid, an uncharacteristic designation for a tropical latitude. This surprising dryness is primarily due to the influence of cold currents that suppress rainfall over the lowlands for much of the year.
Air temperatures remain moderate, generally ranging from the low 20s to around 30 degrees Celsius (mid-60s to high 80s Fahrenheit) across the seasons. This range is significantly cooler than other landmasses found along the equatorial belt. Humidity levels are variable, shifting with the seasons, but the lowlands often appear desert-like, with scant annual precipitation.
The Two Distinct Seasons
The climate of the Galápagos is divided into two main periods. The Warm and Wet Season typically runs from December through May. During this time, air and sea temperatures are at their warmest, with water temperatures peaking around 25°C (77°F).
This season is characterized by clearer, sunnier skies, and the islands receive the majority of their annual precipitation. Rainfall usually occurs as brief, heavy tropical downpours, often in the afternoon. Sea conditions are generally calmer, offering excellent visibility for marine activities.
The Cool and Dry Season, often referred to as the garúa season, lasts from June through November. Air temperatures are noticeably cooler, hovering around 23°C (74°F), and the waters reach their lowest temperatures, sometimes dipping as low as 16°C (61°F). This period is defined by a persistent, low-lying cloud cover and mist, especially over the highlands.
The lowlands receive very little rain, contributing to the “dry” label, but the frequent mist, known locally as garúa, keeps the higher elevations moist. Stronger trade winds during this season can also make the seas choppier, contrasting with the warm season.
Influence of Ocean Currents
The archipelago’s climate is directly controlled by the flow of three major ocean currents intersecting at the islands. The cold, nutrient-rich Humboldt Current, originating in the Antarctic, travels north along the coast of South America before veering toward the islands. The strength of this current dominates the cool and dry season, bringing cold water that chills the air and suppresses evaporation, leading to the characteristic mist.
The Humboldt Current’s influence wanes from December to May, allowing the warmer, shallower Panama Current to become dominant. This current flows from the Central American basin and brings warmer waters to the archipelago, directly causing the warmer air and sea temperatures of the warm and wet season. The shift in dominance between the cold Humboldt and the warm Panama Currents is the primary driver of the seasonal climate cycle.
A third, year-round influence is the deep, cold Cromwell Current, also known as the Pacific Equatorial Undercurrent. This current flows eastward beneath the warmer surface layers and is rich in nutrients gathered from the deep ocean. When the Cromwell Current collides with the submerged western slopes of the islands, it forces the cold, nutrient-dense water to the surface in a process called upwelling. This constant upwelling sustains the high marine productivity and allows cold-water species, like penguins, to thrive in this equatorial setting.
Microclimates and Elevation
Beyond seasonal changes, the volcanic topography of the larger islands creates significant variations in weather and vegetation across short distances, resulting in distinct microclimates. The coastal zones are arid and hot, receiving very little direct rainfall, leading to a landscape dominated by drought-resistant vegetation and cacti. These lower areas often lie in a rain shadow, remaining dry even during the warm, wet season.
As altitude increases on islands like Santa Cruz and Isabela, the climate undergoes a dramatic transition. The moist, low-lying cloud layer (garúa) condenses against the mountain slopes, providing a continuous source of moisture to the highlands. This moisture supports lush, dense vegetation zones, such as the Scalesia forest, which stand in stark contrast to the barren coasts below. The humid highlands are cooler and receive much greater effective precipitation than the lowlands.