SAN JOSÉ, Costa Rica — The passage of Tropical Wave No. 40 across Costa Rica is expected to significantly increase atmospheric moisture and instability this Sunday afternoon, bringing widespread rain and thunderstorms, according to the National Meteorological Institute (IMN).

Afternoon Forecast: Thunderstorms and Regional Impacts

Early morning weather patterns recorded maritime rain on both coasts. While mainland conditions began partially cloudy in the Caribbean and sunny in the Pacific, afternoon hours will see scattered showers in the Caribbean and heavy downpours with thunderstorms in the South Pacific.

Lighter precipitation is forecast for the Central Pacific, North Pacific (central and western areas), and sectors of the Central Valley. Wind gusts are also expected in the northern Pacific coast.

“This type of precipitation cannot be ruled out in the mountains of the Caribbean and south of the Northern Zone. Moderate winds in the northern part of the North Pacific will occur during periods of the day.”

Dry September: El Niño Suppresses Seasonal Rainfall

Despite Sunday’s rains, IMN confirms that a rainfall deficit will persist through late September and early October across the Pacific, Central Valley, and Western Northern Zone due to El Niño and stronger-than-normal trade winds.

“This deficit condition is due to an established underlying El Niño phenomenon, along with atmospheric conditions that generate stronger-than-normal trade winds…”

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