People gather at Sydney's Bondi Beach during a heatwave that hit Australia's largest city, November 20, 2015. Reuters/Jason Reed

A hot air mass, also known as heatwave, is moving across Australia's southeast regions and is predicted to cause the mercury to hit 34 in several parts of the nation. The country will witness the hottest night on Tuesday in 44 years since 1972.

At 10 am on Tuesday, Sydney’s temperature was recorded as 35C and was expected to grow further to 39C. Temperature in Melbourne as well as Adelaide is expected to be around 34C. The effect is likely to sizzle Australia's southeast regions for two days (Dec. 13 and 14).

“We are going to have generally hot and dry northwesterly winds associated with these warm temperatures,” said Sarah Chadwick, Bureau of Meteorology forecaster.

Fire ban declared in several regions of Australia

A fire ban has been declared in various regions of the country, including Victoria's north and west, Illawarra and Shoalhaven, Riverina regions, far south coast, lower central plains and southern slopes, as the temperature is likely to rise up to 39C.

A 34-year-old man was arrested yesterday for starting a snub fire in western Sydney.

The effect of this temperature will subdue on Wednesday night

Australia will most likely witness relief on Thursday as the temperatures are expected to drop to 22C on the day.

Heatwave Australia: Things you should know to prepare for the hot weather

According to the Bureau of Meteorology, a heatwave is a period, mostly stretching over three days, when the combined effect of heat stress and excess heat are unusual for a local climate.

Are heatwaves dangerous? Can they cause death?

People already suffering from exacerbate conditions have higher risk of heat cramps, heat exhaustion and life-threatening heat stroke.

History reflects that Australian heatwaves can be deadly. It has been reported that 4,555 people have died of extreme heat in the country between 1900 and 2011. Australian heatwaves are considered as one of the most dangerous natural hazards for the country.

Precautions to avoid heatwave

It is advisable to stay inside as much as possible and avoid going under the sun. Wet towels may be used for keeping cool. Also, drink plenty of water to stay cool and hydrated. Avoid labourious activities. Take care of pets and avoid leaving them in hot cars during heatwave in Australia.