Heat alerts as much of Australia set to sizzle

Australians are being warned to prepare for a heatwave that is expected to grip many parts of the country for days.

Much of New South Wales and parts of Queensland, South Australia, West Australia, the Northern Territory and Australian Capital Territory are predicted to cop soaring temperatures until Friday.

NSW residents are in for a sweltering period with a severe heatwave warning issued from Wednesday which is expected to last for the next three days.

Residents in the northern tablelands, central west slopes and plains and lower and upper western districts are being warned by the Bureau of Meteorology about above average maximum temperatures, with some areas tipped to reach the high 30C to low 40C.

The Illawarra, Hunter and Riverina regions were also issued with a severe heatwave warning.

No total fire bans were declared but the NSW Rural Fire Service urged people in bushfire prone areas to have an action plan ready in the case of an emergency.

NSW Health also warned about the effects of heatwaves on vulnerable people, including those over 65 years, babies, young children, pregnant women and the homeless.

People are being urged to avoid being outdoors during the hottest part of the day, to wear sunscreen, sunglasses and hats and stay hydrated.

NSW Police reminded commuters to keep their cool on the roads, particularly if there were traffic delays.

"We know many people will want to head to the beach, a local swimming hole or swim in your backyard pool, please be careful," a NSW Police spokesperson said.

"Keep a watchful eye over children especially when they are near the water, all children need to be supervised."