National weather projections by IMN
Costa Rica is expected to enter the 2026 rainy season with an irregular onset and overall below-normal rainfall in many regions, according to projections from the Instituto Meteorológico Nacional (IMN). While the first rains may occur between April and May, as is typical, they are not expected to consolidate uniformly across the country, and overall precipitation totals could be 10 % to 30 % below average through much of the year, especially later in the season.
Staggered start of the rainy season by region
According to the IMN’s climate outlook, the onset of rain in 2026 will vary geographically:
• Southern Pacific: between April 27 and May 2
• Central Pacific: between May 2 and May 10
• Central Valley: between April 29 and May 8
• Northern Pacific: between May 8 and May 13
• Northern Zone: between May 11 and May 13
• Caribbean: possibly without a clearly defined dry season before rains begin
This staggered pattern suggests that although rainfall may occur intermittently, the overall rainy season is likely to be uneven and delayed in some areas rather than uniformly established nationwide.
Temperatures and atmospheric conditions
In addition to rainfall patterns, the IMN has noted higher-than-normal temperatures in various parts of the country during 2026, associated with seasonal shifts and typical dry-season atmospheric conditions. These warmer conditions, coupled with lower rainfall, may lead to higher heat indices and greater aridity in some regions, which could affect agricultural planning, water resources, and climate-related risk management.
Implications for society and sectors
The forecast of an irregular and potentially drier rainy season has important implications for agriculture, water management, wildfire prevention, and tourism. Reduced rainfall can prolong dry and warm spells, while abrupt changes in precipitation patterns may present logistical challenges for farming and rural infrastructure planning.
Official and reference sources
• The Tico Times, “Costa Rica faces drier, hotter 2026 as IMN sees uneven start to rainy season” — overview of climate expectations for 2026.
• Instituto Meteorológico Nacional (IMN) — climate outlook and regional rainfall projections for 2026.
• La Nación, report on the expected start dates of rainfall by region according to the IMN.
