Metro Manila (CNN Philippines) — Expect more rains as summer comes to a close.

Weather forecasters said Wednesday (May 18) they see the rainy season beginning in early June.

"Later on, the rainfall will be more frequent and there will be a very significant build up of cloudiness," said Anthony Lucero, Monitoring and Prediction Section chief of the Philippine Atmospheric Geophysical and Astronomical Services Administration (PAGASA).

But with the El Niño episode expected to prevail until July, will it have an impact on the weather pattern?

While it will lessen the normal amount of rainfall during the wet season, PAGASA said it may actually bring relief from floods.

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Lucero said floods occur during the peak of the rainy season but with the El Niño interrupting the normal weather pattern, these may not occur.

But water regulators are not taking chances.

The National Water Resources Board (NWRB) said effective management of Angat Dam's water level will continue to ensure sufficient supply for all consumers.

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Angat Dam is the main water source for Metro Manila.

"Although may pag-ulan na darating, we're still in El Niño. 'Pag ganito, though may pag-ulan, mas mababa pa rin sa normal," said Sevillo David, executive director of the NWRB.

[Translation: Although the rains will come, we’re still in El Niño. In this case – though there will still be rains – but below the normal level.]

But there could be another threat to the country before the year ends.

PAGASA said a La Niña episode may prevail by December, which will bring more than the usual amount of rainfall, increasing the potential for floods and landslides.

Provinces in the eastern part of the country, which includes Isabela, Quezon, Bicol, Samar, Leyte, Mindoro, Surigao, and Agusan, are most vulnerable.

The weather bureau advises communities and local officials to prepare as early as now.