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Authorities urged residents to avoid rivers and lakes during periods of heavy rain due to the high risk of flooding. Photo courtesy of Costa Rica Fire Department.

Tropical Wave To Increase Rainfall Across Costa Rica

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Published on Thursday, August 20, 2026

By the A.M. Costa Rica staff

According to the National Meteorological Institute (IMN), Tropical Wave No.34 is expected to bring heavy rain and thunderstorms to much of Costa Rica through Friday as it moves across the country.

The system was moving along Panama’s Caribbean Coast Thursday and was expected to enter Costa Rica that night, where it would pass through within about 24 hours, according to meteorologists.

The wave is expected to pass quickly, but lingering moisture could keep showers in the forecast through Friday. Conditions should gradually improve Saturday, according to the IMN.

Last weekend, flooding along Costa Rica’s Caribbean Coast and in the northern part of the country prompted the National Commission for Emergencies (CNE) to take emergency measures. Hundreds of people were moved to shelters, public schools were closed, thousands of homes lost electricity, and several roads were shut down.

The IMN forecast the following rainfall totals across the country:

Central Mountain Range: 50 to 100 millimeters, with the heaviest rainfall expected at higher elevations.

Pacific Coast, including Guanacaste Province and Puntarenas Province: 30 to 60 millimeters.

Central Valley, including San José, Alajuela, Heredia and Cartago: 30 to 50 millimeters.

Caribbean Coast, including Limón: 60 to 80 millimeters, with thunderstorms likely.

The CNE issued an Orange Alert, the third-highest level on the country’s emergency alert scale, for northern areas of Alajuela, Heredia and Limón provinces.

The alert reflects the ongoing risk of heavy rainfall and potential flooding and requires emergency response teams to remain on high alert and prepared for worsening conditions.

Authorities also issued a Yellow Alert for San José, Cartago and Puntarenas provinces. A Yellow Alert, the first level of the country’s warning system, requires local emergency committees to closely monitor conditions because of the increased potential for an emergency.

As of Wednesday, authorities had not issued a weather alert for Guanacaste Province.

Meanwhile, the Ministry of Public Works and Transportation (MOPT) is maintaining a precautionary advisory for Route 32, the main highway linking San José and Limón. Authorities warned that overnight closures remain possible because of heavy rainfall and the risk of landslides.

Drivers were advised to use alternate routes, including Route 10 through Turrialba canton (Cartago) and onward to Siquirres canton (Heredia), before reconnecting with Route 32 toward Limón. MOPT said it will post traffic updates through its official social media channels.

Authorities urged residents to take several precautions during the storm, including:

Avoid rivers and lakes during periods of heavy rain.

Monitoring mountainous areas for landslides and falling debris.

Residents in flood-prone communities are urged to review evacuation plans.

Drivers were warned to watch for flooding, slippery roads and reduced visibility.

Remain alert for strong winds that could bring down trees or power lines.

Stay indoors during thunderstorms and avoid using electronic devices during lightning activity.

Call 911 to report flooding, landslides or fallen trees.

Costa Rica has a tropical and subtropical climate with two primary seasons. The dry season, commonly referred to as summer, typically runs from December through May. The rainy season extends from June through November and generally coincides with the Atlantic hurricane season.

The CNE recently issued an alert for parts of the Pacific Coast due to an anticipated reduction in rainfall. However, meteorologists cautioned that the arrival of tropical waves can still trigger periods of heavy precipitation across much of the national territory.

The U.S. Embassy in San José recently issued a warning to American citizens visiting Costa Rica to take extra precautions during the country's rainy season.

The IMN is Costa Rica’s government agency responsible for issuing weather forecasts, hazardous weather warnings and related public safety information.

CNE works in partnership with communities and emergency responders to strengthen the nation’s preparedness, response, and recovery from natural hazards.

MOPT is the government agency responsible for managing the country’s roads, ports, and airports, as well as overseeing public transportation policy.

A.M. Costa Rica encouraged readers to share the weather advisory with their networks

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Have recent rains caused emergencies in your community? We would like to know your thoughts on this story. Send your comments to news@amcostarica.com