MANILA -- Rotational brownouts threaten parts of Luzon for a second straight day on Thursday due to insufficient power reserves, power distributor Meralco said.

Power outages may be implemented between 10 a.m. to 4 p.m., and could last for 1 to 2 hours per area, said Meralco spokesperson Joe Zaldarriaga told DZMM. Affected areas will be identified in the distributor's social media pages at around 9 a.m., he said.

The Luzon grid was placed red alert, the highest warning, from 10 a.m. to 4 p.m. The second highest alert, yellow, was raised from 8 a.m. to 10 a.m. and again at 4 p.m. to 9 p.m., according to the National Grid Corp of the Philippines.

The NGCP estimated peak demand at 10,607 megawatts against available capacity of 10,761 megawatts.

The public can help prevent brownouts by avoiding opening refrigerators unnecessarily, cleaning electric fans and air-conditioning vents, and unplugging unused appliances, Meralco earlier said.