The hottest time in Vietnam usually falls in June, but this April has seen a heat wave sweep the country, and Hanoi has not been spared.

In the capital city, the average temperature in April was about 24 degrees Celsius.

But last Saturday, Hanoi peaked at 38.9 degrees (102 degrees Fahrenheit), Nguyen Van Huong, head meteorologist at the National Center for Hydro-Meteorological Forecasting, told local media.

This surpassed the record of 38.5 degrees Celsius in April 1919, the national weather office said. The city's temperature is 33 degrees on Friday, forecast to rise to 36 on Monday.

The years 2003, 2012 and 2015 also saw above average temperatures in Hanoi.

Huong said, as cited by Lao Dong newspaper, that temperatures in northern Vietnam since early April this year have increased by two to three degrees higher than the average of 23-34 degrees Celsius.

Record temperatures have been recorded in many parts of the country.

Most notably, Huong Khe District in the central province of Ha Tinh, 361 km south of Hanoi, experienced the nation's highest ever recorded temperature at 43.4 degrees Celsius (110 degrees Fahrenheit) last Saturday.

Huong said the main reason for the extreme heat was a combination of the impact of El Nino and global warming, not to mention urbanization.

The impact of El Nino is mainly evident in the first half of the year and not so pronounced in the second half. Therefore, Huong told local media that the average temperatures this summer would be about 0.5-1 degrees higher than the normal average.

He said it was very likely that the heat wave will set new records of 39-41 degrees or even higher, but the peak experienced in Ha Tinh was not likely to be repeated.

The weather office has warned of more heat waves in the coming months. It has said that the northern and central regions will suffer from more hot temperatures between April and August, longer than other regions in the country.

A study published in the journal Climatic Change last September said Southeast Asian countries like the Philippines and Vietnam would be most affected by heat-related mortality along with countries in Southern Europe and South America.