The Philippine Institute of Volcanology and Seismology (PHIVOLCS) issued a lahar advisory for Mount Pinatubo and Taal Volcano on 29 August 2026.

According to PHIVOLCS, based on the Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) Heavy Rainfall Warning No. 15 issued at 11 a.m. on Saturday, southwest monsoon rains will continue to affect the western and central portions of Luzon.

The advisory said the rains could generate volcanic sediment flows or lahars, muddy streamflows and muddy runoff in rivers and drainage areas around Mount Pinatubo and Taal Volcano.

“DOST-PHIVOLCS thus strongly recommends increased vigilance and readiness of communities in pre-determined zones of lahar and related hazards on these volcanoes.”

The agency said prolonged and intense rainfall may generate non-eruption lahars on major rivers draining western Mount Pinatubo, where significant deposits from the 1991 pyroclastic density currents remain in the watershed.

“Pinatubo lahars are likely to be channel-confined and occur on the upper to middle reaches of the Sto. Tomas-Marella and Bucao River systems but may transition to muddy streamflows and floods on the lower reaches and affect adjacent communities of San Marcelino, San Narciso, San Felipe and Botolan, Zambales Province.”

“Muddy streamflows may likewise be generated along the O’Donnell and Pasig-Potrero River systems draining the Pinatubo edifice to the north and southeast, respectively, and affect downstream communities in Tarlac and Pampanga Provinces.”

PHIVOLCS also said prolonged and heavy rainfall may generate muddy streamflows, muddy runoff and even volcanic debris flows around Taal Volcano, particularly on the slopes west and north of Taal Lake.

Old and loose volcanic deposits, already saturated from previous rains, may be remobilized in streams, roads and across lakeward slopes.

In particular, muddy and debris flows can recur in previously affected communities of Agoncillo, Laurel and Talisay in Batangas.

“DOST-PHIVOLCS strongly advises the communities and local government units of the above identified areas of risk to continually monitor the storm conditions and take pre-emptive response measures for their safety.”