Costa Rica Braces for Drier 2026 Rainy Season as El Niño Returns with 60% Probability Summary

The IMN predicts Costa Rica’s 2026 rainy season will see 10% to 30% less rainfall and higher temperatures due to a 60% chance of El Niño returning by mid-year.

By: AXL Media

Published: Apr 20, 2026, 10:17 AM EDT

Source: The Tico Times

An Irregular Transition to the Green Season

Costa Rica’s transition into the 2026 rainy season is expected to be characterized by inconsistency rather than the traditional sudden shift. According to the Instituto Meteorológico Nacional (IMN), the southern and central regions will likely experience the arrival of rain first, while northern territories will face a delayed onset. This patchy start suggests that despite the calendar change, many provinces will remain in a state of transition for longer than usual, complicating agricultural planning and water resource management for the second quarter of the year.

The Strategic Impact of El Niño’s Return

The primary driver behind the projected water deficit is the high probability of an El Niño Southern Oscillation (ENSO) event. Forecasters place the odds of El Niño developing by mid-2026 at approximately 60%, a figure supported by NOAA’s recent ENSO discussions. For the Pacific slope and the Central Valley, this typically results in suppressed rainfall and increased solar radiation. The IMN warns that the most significant shortfalls will likely occur between September and November—traditionally the wettest months of the year—with a 30% reduction in precipitation possible in some sectors.

Temperature Spikes and Thermal Stress

In addition to reduced rainfall, 2026 is shaping up to be a year of record-breaking heat. Temperatures are projected to run 1 to 3 degrees Fahrenheit above climatological norms, with the North Pacific region (Guanacaste) expected to bear the brunt of the thermal increase. This rise in temperature, combined with lower humidity, increases the risk of wildfires and places additional stress on the national power grid, which relies heavily on hydroelectric generation. The IMN emphasizes that even during active rain days, the "heat feel" will likely remain elevated.