El Niño Could End Costa Rica’s Rainy Season Early This Year

If you live on Costa Rica’s Pacific side, the rainy season may end sooner than you’re used to this year. The National Meteorological Institute (IMN) expects El Niño to cut the wet season short, with the dry season settling over the Pacific coast and the Central Valley between October and December. September has already come up short as The IMN projects the month will close with 80% less rain than normal in the North Pacific, which includes Guanacaste. The Central and South Pacific are tracking about 60% below normal, and the Central Valley about 50%. That matters because this is normally the wettest stretch of the year. It’s when rivers, wells and aquifers refill before months of almost no rain. A short, weak rainy season leaves less water stored for the dry months ahead. The IMN has not set a date yet, and November is still expected to be the month of transition. In a typical year, the dry season reaches the North Pacific around mid-November, then spreads to the Central Valley, Central Pacific and South Pacific over the following weeks. Some years, the switch drags into December. Last year, the rains ended in the last week of November in the North Pacific, Central Pacific and Central Valley. The South Pacific dried out in the first week of December. The Caribbean is the exception. The IMN projects September rain about 20% above average on the northern Caribbean coast and 30% above average on the southern Caribbean, and it expects normal rainfall there through December. If you’re heading to Limón, Cahuita or Puerto Viejo, pack for rain, because that side has no real dry season. The northwestern Northern Zone is a different story. The IMN expects rainfall there to run about 30% below normal from October through December. Expect more heat, too. The IMN projects September’s average temperature at 1.5°C to 2°C (2.7°F to 3.6°F) above normal in the North Pacific, and 1°C to 1.5°C (1.8°F to 2.7°F) above normal across the rest of the country. It also expects fewer and later cold fronts this year, which means fewer of the cool, breezy spells that usually take the edge off the heat late in the year. Today, the IMN forecasted a high of 37.1°C (98.8°F) in Liberia and 29.5°C (85.1°F) in San José. Don’t read the heat as a promise of clear skies as hot mornings with weak winds still build afternoon storms, and the IMN warned that very localized heavy downpours remain possible. That pattern is typical of El Niño since instead of steady rain, you get long dry spells broken by short, intense bursts, which is why a heavy afternoon storm doesn’t mean the shortage is over. The ocean explains why this year is so extreme as in August, sea-surface temperatures in the tropical Pacific ran close to 2.5°C (4.5°F) above normal, higher than at the same point in the 1997 and 2015 events, according to the IMN. The institute expects El Niño to keep strengthening toward the end of 2026. The shortage has already triggered emergency alerts. On Sept. 18, the National Emergency Commission (CNE) raised all 11 Guanacaste cantons to orange alert, along with Central Pacific cantons including Garabito, Parrita and Quepos and the Los Santos coffee region. An orange alert tells public agencies to move from watching the situation to actively responding to it. Water is the main worry. Rationing has already reached communities on the Pacific side, and national planners have warned of wider supply risks in the months ahead. If you live in Guanacaste or the Central Pacific, check whether your water provider has a rationing schedule, keep some water stored for outages and fix leaks now. The IMN says it will set dates for the start of the dry season as the transition approaches. Until then, forecasters expect the Pacific slope and the Central Valley to stay hotter and drier than normal.