The National Meteorological Institute (IMN) reported that the first tropical wave of the rainy season will hit Costa Rica on Thursday evening.
Heavy rains are expected to begin in the Caribbean region, and then will spread to the rest of the country.
The report also says that current weather conditions favor heavy rainfall accompanied by thunderstorms.
The most intense downpours expected on Thursday and Friday likely will occur in the Pacific region and the Central Valley.
The IMN urged residents to remain alert for possible floods in urban areas and to maintain vigilance near rivers.