Tropical Wave #23 made landfall on Costa Rica's coast on August 14, 2025, bringing intense rainfall and strong winds to several regions, with the Sarapiquí area being particularly affected. The passage of this wave, combined with the Intertropical Convergence Zone (ITCZ), created highly unstable atmospheric conditions, resulting in widespread heavy downpours and thunderstorms across the country. The National Meteorological Institute (IMN) confirmed that the interaction between Tropical Wave #23 and the ITCZ generated significant atmospheric instability, a characteristic of the ITCZ's seasonal migration which influences Costa Rica's wet and dry seasons. The ITCZ, a belt of low pressure near the equator where trade winds converge, is known for producing substantial rainfall and thunderstorms in tropical regions due to the rising, cooling, and condensing of air masses.
The immediate consequences of the tropical wave included emergencies such as fallen trees and damage to homes, with images of the impact widely shared on social media. Costa Rica's disaster management system, led by the National Commission for Risk Prevention and Emergency Response (CNE), is in place to address such events. This preparedness includes regular drills and collaboration between governmental and non-governmental organizations, aiming to mitigate the effects of weather-related disasters, which pose a significant risk to the nation. Costa Rica historically experiences considerable rainfall, with an average of approximately 100 inches annually, and some areas receiving much more. The ITCZ's position typically dictates the country's rainy season from May to November and a dry season from December to April, though microclimates can alter these patterns. The Sarapiquí region, for example, is known for its consistently wet climate. The nation has also secured international support, including a $350 million loan from the World Bank, to enhance its resilience against natural hazards and climate change impacts, crucial measures given the potential for significant economic damage from weather events, as seen in past occurrences like Tropical Storm Nate.