High temperatures in northern provinces like Lang Son, Bac Ninh, Bac Giang, Hai Duong, Hung Yen, Ha Nam and Ninh Binh were recorded at 39 degrees Celsius on Monday while those in Hanoi and Hoa Binh reached 40 degrees Celsius, according to the National Center for Hydro-Meteorological Forecasting.

The heat wave is forecast to linger until June 13 and may become the longest to have hit northern Vietnam since 1993.

Nguyen Van Huong, head of the weather forecasting department at the center, said widespread heat waves since 1993 had only lasted five to seven days.

The average temperatures in northern localities in the coming days are expected to reach 36 to 39 degrees Celsius. American forecast services provider AccuWeather said the temperature in Hanoi would reach 38 degrees Celsius and remains at 35-36 until this weekend.

At 1 p.m. Monday, all monitoring stations recorded temperatures above 37 with a scorching hot sun. The highest is Lang area at 39, Ha Dong District at 38.5, Hoai Duc and Son Tay Districts at 38.

The heat wave was caused by low-pressure areas from the west and the Foehn wind, a type of dry, warm and down-slope wind that occurs in the lee of a mountain range, Huong said.

Experts have advised residents to avoid direct exposure to sunlight between 10 a.m. and 3 p.m. and to wear sunscreen, sunglasses and brimmed hats if venturing out under the sun.

Central Vietnam has been impacted by similar scorching weather over the past 10 days. The heat is expected to continue in the region until June 16.

It is quite common for a heat wave to last 17 to 18 days in central Vietnam. The most intense heat wave to have struck the region occurred in 2015, lasting for up to 39 days.

The National Center for Hydro-Meteorological Forecasting has warned of high risks of fire and explosion at local residential areas and forests due to the hot and dry weather.

Vietnam has been going through scorching days since early May.

On May 21, Hanoi's Ha Dong District experienced a record 40.9 degrees Celsius, the highest May temperature since 1961. On the same day, parts of Lao Cai, Hoa Binh and Ha Giang also recorded their highest May temperatures in decades. 

Last year, Vietnam went through possibly the hottest summer in history with average temperatures 0.5-1 degrees Celsius higher than previously, climbing to an average 39-42 degrees Celsius in many parts of the country. The nation broke its highest temperature record on April 20 as the mercury hit 43.4 degrees Celsius, or 110 degrees Fahrenheit, in Huong Khe District, Ha Tinh Province in central Vietnam.