Southeast Asia is grappling with a brutal heatwave as record-high temperatures have led to school closures and triggered urgent health warnings across the region.

Millions of students across the Philippines were ordered to stay home on Monday after the authorities cancelled in-person classes for two days. The Department of Education ordered students of more than 47,000 public schools to switch to home-based, online lessons.

The main advice for people across the country was to avoid outdoor activities and drink plenty of water, but the young and the elderly were told to be especially careful.

The sweltering weather also led to fears of water shortages, power outages and damage to crops.

Large crowds sought relief in air-conditioned shopping malls in metropolitan Manila, the congested capital of more than 14 million people where the temperature soared to 38.8 degrees Celsius (101.84 degrees Fahrenheit) on Saturday, surpassing the record set decades ago, according to weather officials.

The country’s weather agency said the heat index – the actual temperature felt by the body to include relative humidity – is expected to remain at a record 45C (113F), in the range which it classes as “dangerous” as conditions can trigger heatstroke from prolonged exposure.

This year, Cambodia has been facing the highest temperatures in 170 years, Chan Yutha, a spokesperson for the Ministry of Water Resources and Meteorology, told The Associated Press news agency. The ministry has forecast that temperatures in most parts of the country could reach up to 43C (109F) this week.

Myanmar’s Meteorological Department said seven townships in central Magway, Mandalay, Sagaing and Bago divisions experienced unprecedented high temperatures.

In northern Thailand, temperatures have topped 44C (111F) in some areas, while the capital, Bangkok, and the metropolitan areas have witnessed temperatures above 40C (104F). The forecast from the Meteorological Department said this year’s summer, which usually lasts from late February to late May, is expected to be 1-2C (1.8-3.6F) hotter than last year’s, and rainfall will be lower than average.

Thailand’s Department of Disease Control said last week at least 30 people have died from heatstroke so far this year, compared with 37 for all of last year.

Vietnam’s national weather agency warned of the risks of forest fires, dehydration, and heat shock, while the state electricity company urged consumers to refrain from overworking their air-conditioning units, warning that electricity consumption has reached record highs in recent days.

Scientists have said the number of heat-related deaths around the world has been rising significantly in recent years along with temperatures. However, the trend in Asia so far is unclear, partly because of the question of how to classify deaths that appear to be heat-related.