Hundreds of schools in the Philippines, including dozens in the capital Manila, suspended in-person classes on Tuesday due to dangerous levels of heat, education officials said.

The country’s heat index measures what a temperature feels like, taking into account humidity.

The index was expected to reach the “danger” level of 42 degrees Celsius in Manila on Tuesday and 43C on Wednesday, with similar levels in a dozen other areas of the country, the state weather forecaster said.

The actual highest recorded temperature for the metropolis on Tuesday was 35.7C, below the record of 38.6C reached on May 17, 1915.

Local officials across the main island of Luzon, the central islands, and the southern island of Mindanao suspended in-person classes or shortened school hours to avoid the hottest part of the day, education ministry officials said.

The Department of Education was unable to provide an exact number of schools affected.

March, April and May are typically the driest months of the year for swathes of the tropical country. This year conditions have been exacerbated by the El Nino weather phenomenon.

Primary and secondary schools in Quezon, the most populous part of the capital, were ordered to shut while schools in other areas were given the option by local officials to shift to remote learning.

Some schools in Manila also reduced class hours.

A heat index of 42-51C can cause heat cramps and exhaustion, with heat stroke “probable with continued exposure”, the weather forecaster said in an advisory.

Heat cramps and heat exhaustion are also possible at 33-41C, according to the forecaster.

The orders affected hundreds of schools in the Mindanao provinces of Cotabato, South Cotabato and Sultan Kudarat, as well as the cities of Cotabato, General Santos and Koronadal, Zamboanga regional education ministry spokeswoman Rea Halique told AFP.

Five schools in Mindanao’s Zamboanga region also shut schools for the day, though local officials in the area did not recommend the suspension of in-person classes in other schools, the ministry said.

“At the Pagadian City Pilot School one (kindergarten) student and two in the elementary school suffered nosebleeds,” Zamboanga regional education ministry official Dahlia Paragas told AFP.

“All of them are back at home in stable condition and were advised to avoid exposure to the sunlight.”

Cotabato city experienced the highest heat index in Mindanao, reaching 42C on Monday and Tuesday, the state forecaster reported.