The Instituto Meteorológico Nacional said Wednesday that another tropical wave would pass over the country today.
The waves are long troughs of low pressure running north to south. They have been credited with the heavy rains that have hit the northeastern part of the country since June 20.
Some rain and thunderstorms were reported in the southern part of the country Wednesday night.
The weather institute said that some rain was expected in the province of Limón early today and that the rain would increase during the day.
Rain would not become heavy in the Central Valley and the Pacific coast until the afternoon, the forecast said.
The weather institute issued a bulletin about the tropical wave at mid-afternoon and followed up with an evening forecast.
The waves are a product of winds in Africa, and they travel east to west around the globe at tropical latitudes.