Commuters try to catch a ride after a thunderstorm in Cubao Quezon City on June 6, 2023. Jonathan Cellona, ABS-CBN News/File

QUEZON CITY - State meteorologists said that the frequent afternoon and evening thunderstorms signal the transition from the warm and dry season to the rainy season in the Philippines. 

Since the beginning of May, northern and central Luzon as well as Mindanao have been experiencing thunderstorms. 

However, senior weather specialist Rusy Abastillas of the Climate Monitoring and Prediction Section said it will take more than thunderstorms to declare the start of the rainy season. 

Below normal rains seen until July despite La Niña: PAGASA  

"Wala pa tayong westerly component ng wind na minomonitor kasi iyon ang isa sa mga criteria doon sa ating onset [ng rainy season] - dapat merong westerly [winds]," she told ABS-CBN News on Wednesday. 

(There is no westerly wind [southwest monsoon] component yet, which is required for the declaration of the start of the rainy season.) 

Even with the transition already on its way, the beginning of the rainy season may be slightly delayed because of a developing La Niña. 

"Ang impact kasi ng La Niña 'pag pre-developing... transitioning from El Niño to La Niña, 'yung ang nagbibigay minsan ng delay sa onset tapos instead of expecting the above normal rainfall ang ating inaasahan 'pag may La Nina na, below normal during the Habagat season," Abastillas said. 

62 pct chance of La Niña in June: DOST  

She said the onset of the rainy season may happen in June, instead of the second half of May. 

In an advisory issued on May 6, PAGASA said El Niño continues to weaken and may move to a neutral condition around June before shifting to La Niña by July. 

Abastillas however said an updated forecast shows that the climate phenomenon may also be delayed and come in around July-August-September season. 

El Niño and La Niña are the warm and cold phases, respectively, of a naturally occurring climate pattern called El Niño-Southern Oscillation (ENSO). 

ENSO is exhibited through changes in the wind strength and direction and sea surface temperatures of tropical Pacific Ocean with wide-ranging impacts on global climate. 

In the Philippines, El Niño leads to less rains and storms while La Niña, above-normal rains and more tropical cyclones forming near the country. 

El Niño weakens; La Niña Watch issued 

So when can the above-normal La Niña rains be expected? 

"Doon na siya magstart na ang impact na above-normal rainfall during the last quarter [of this year] up to the first quarter [of 2025] during Amihan (northeast monsoon) season. Usually doon ang impact ng mas maraming ulan at may mga baha," Abastillas said. 

The most vulnerable areas to the above-normal rains are the eastern sections of the country - which include Cagayan Valley, Aurora, Quezon, Bicol Region, Eastern Visayas, Caraga, and Davao Region. 

Prior to the the 2023-2024 El Niño, a rare triple-dip La Niña occurred. 

Triple dip means that the large-scale cooling of the Pacific Ocean spanned three years - from July 2020 through March 2023.

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