San José, Costa Rica, since 1956
Rainy season

Low rainfall in Central Valley, northern regions; La Niña still a no-show

An increase in rainfall levels expected for August due to the pending influence of a La Niña weather phenomenon did not occur, the National Meteorological Institute (IMN) confirmed.

Earlier this year, the IMN predicted that precipitation levels would return to normal after a dry 2015 rainy season. But, rainfall has been lower than expected this year and lower than the monthly average in various regions.

During August, the Central Valley, Northern Zone and central Caribbean have received 37 to 72 percent less rain than normal, IMN’s Meteorologist Luis Fernando Alvarado said. The driest places were the capital San José, the northwestern province of Guanacaste and the northern Alajuela cantons of Upala, Los Chiles and Guatuso.

Accumulated rainfall in all other regions of the country was within the expected ranges, Alvarado said.

An IMN report in June predicted that La Niña would likely cause an increase in rains starting in July, by some 30 percent overall and up to 70 percent in Guanacaste, with above-average rainfall along the Pacific coast and in the Central Valley.

Now, forecasters think La Niña will develop and strengthen in the coming months, though the weather phenomenon will likely be shorter and less intense than expected.

Weekly forecast

Despite the delay, IMN experts are expecting an increase in general rainfall levels starting this week, along with an increase in relative humidity and atmospheric instability.

These conditions will likely cause warmer temperatures during the mornings that will favor conditions for moderate to high intensity showers during the afternoons and evenings, mainly along the Pacific coast and in the Central Valley.

IMN also expects occasional showers in the Northern Zone and in the mountains of the Caribbean region.

High winds toward the end of the week are expected to bring heavy rains to the central and southern Pacific regions. IMN also expects scattered showers for the northern Pacific region.

Meteorologists said they expect rainfall levels to keep intensifying in the coming weeks.

Contact L. Arias at

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