A strong El Niño has taken hold over Costa Rica and will keep much of the country drier and hotter than normal through the rest of 2026, according to the Instituto Meteorológico Nacional (IMN), which expects the warm phase of the El Niño–Southern Oscillation to persist into early 2027.
The institute’s early-warning system for the phenomenon has moved from watch to advisory, the threshold at which forecasters treat the event as essentially certain rather than probable, and officials have compared its likely strength to the 2014–2015 episode. The effect falls unevenly across the country: the Pacific slope and the Central Valley face significant rainfall deficits and rising temperatures, while the Caribbean is expected to stay near or above its normal rainfall.
The institute’s projections have grown more severe over the course of the year. In April, IMN director Werner Stolz estimated a nationwide rainfall deficit of between 10 and 30 percent. By mid-year, Karina Hernández, of the institute’s climatology unit, reported a harsher outlook, with the Pacífico Norte, which includes Guanacaste, projected to lose as much as 50 percent of its normal rainfall, and the rest of the Pacific slope, the Central Valley and the northwestern zone — among them San Carlos, Upala and Sarapiquí — running 35 to 40 percent below normal.
Temperatures are expected to sit between 0.5 and 1 degree Celsius (0.9 to 1.8 Fahrenheit) above the historical average, with some scenarios reaching 2 degrees Celsius (3.6 Fahrenheit) above normal. According to the IMN, Guanacaste will register both the sharpest heat and the deepest rainfall losses, with daytime highs in parts of the province approaching 36 degrees Celsius (97 Fahrenheit).
The mechanism behind the split is the warming of the equatorial Pacific that defines El Niño, which suppresses rainfall along Costa Rica’s Pacific slope and the Central Valley while directing more moisture toward the Caribbean. The country has experienced strong El Niño events in 1982, 1997, 2015 and 2023, each of which brought drought, elevated temperatures and disrupted rainfall patterns.
Compounding the phenomenon is the canícula, the midyear reduction in rainfall that ordinarily occurs between mid-July and August. The IMN anticipates a longer and more intense canícula this year, with its most pronounced phase beginning around July 27, when the Pacífico Norte and Pacífico Central are expected to turn especially dry and reduced cloud cover intensifies the heat.
The institute has also warned that Saharan dust, a recurring feature of the season, will arrive more frequently and in heavier concentrations because of El Niño. The specialist Poleo, cited by the institute, said the dust favors clearer, hotter and drier conditions while degrading air quality, and the IMN has flagged a heightened risk for children, older adults and people with respiratory conditions or allergies.
The prolonged deficit carries consequences beyond discomfort. Reduced rainfall strains the reservoirs and aquifers that supply drinking water, prompting the Comisión Nacional de Emergencias earlier this year to prepare a contingency plan and place a large number of cantons under alert, most of them in the Pacífico Norte and Pacífico Central along with a cluster of Central Valley cantons around San José, a measure that raises the likelihood of water rationing in affected areas during the driest weeks.
Lower river levels and reservoir volumes also reduce hydroelectric output, pushing the country toward costlier forms of generation that can be reflected in electricity costs. Agriculture and ranching face stressed pastures and basic-grain crops, and the drier landscape elevates the risk of brush and forest fires, particularly in Guanacaste.
The Caribbean stands as the exception to the national outlook, remaining wet while the rest of the country dries — a contrast that underscores how sharply Costa Rica’s weather divides along its mountain ranges under the influence of El Niño.
