The southwest monsoon or "habagat" and the intertropical convergence zone (ITCZ) will be the dominant weather systems in the country in the next 24 hours, the Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) said on Monday, Sept. 13.

Cloudy skies with scattered rain showers and thunderstorms due to the habagat and ITCZ may affect Batanes, Babuyan Islands, Zambales, Bataan, Abra, Benguet, Ilocos Norte, Ilocos Sur, La Union, Pangasinan, Oriental Mindoro, Occidental Mindoro, Marinduque, Romblon, Palawan, Zamboanga Sibugay, Zamboanga del Norte, Zamboanga del Sur, Basilan, Sulu, Tawi-Tawi, Maguidanao, and Lanao del Sur.

Possible heavy to at times intense rains may affect these areas.

Meanwhile, Metro Manila and the rest of the country will have partly cloudy to cloudy conditions with isolated rain showers due to habagat and localized thunderstorms.

PAGASA said severe thunderstorms, which are often associated with short-lived heavy rains, may also trigger flash floods or landslides.

As of Monday, a gale warning remains in effect over the northern and western seaboards of Northern Luzon due to strong to gale-force winds associated with the southwest monsoon.

"Fishing boats and other small seacraft are advised not to venture out into the sea while larger sea vessels are alerted against big waves," PAGASA said.

Weather specialist Ariel Rojas said there is a slim of tropical cyclone development inside or near the Philippine area of responsibility within two to three days.

However, there is a possibility that a low pressure area may form east of Visayas or Mindanao during the forecast period.

Based on climatological records, PAGASA estimated that two or three tropical cyclones may enter or affect the country in September.

So far, two tropical cyclones have affected the country this month. These were typhoons "Jolina" (Conson) and "Kiko" (Chanthu).