The low pressure area (LPA) spotted east of Northern Luzon has intensified into a tropical depression, PAGASA said.
The state weather bureau said the depression, locally named Henry, was spotted 670 kilometers east southeast of Basco, Batanes as of around 11 p.m. Sunday evening.
It is said to be packing maximum sustained winds of 45 kilometers per hour (kph) near the center and gustiness of up to 55 kph.
PAGASA added that Henry was moving west southwest at 25 kph.
Signal No. 1 is hoisted over Batanes, the northern portion of Cagayan including Babuyan Group of Islands, the northern portion of Apayao, and the northern portion of Ilocos Norte.
PAGASA warned that occasional rains with gusty winds are expected in the areas under the storm warning.
Meanwhile, the southwest monsoon, or habagat, is expected to bring monsoon rain to Zambales, Bataan, Cavite, Batangas, Oriental Mindoro, Occidental Mindoro, Palawan, and Western Visayas.
Scattered rainshowers and thunderstorms will also hit Metro Manila, the rest of Central Luzon, CALABARZON, Marinduque, and Romblon.