Most of NSW has sweltered through temperatures above 40C with residents in the state’s outback copping the worst of the heat as severe conditions continue.

Hay in the Riverina region was the hottest place in NSW on Sunday reaching 45.4C while a blistering 40.3C made Penrith the hottest location in Sydney, the Bureau of Meteorology says.

Much of central and western NSW reached temperatures at or above 40C on Sunday after experiencing similar levels on Saturday.

There’s no relief in sight with temperatures set to increase in western parts of Sydney on Monday and will remain above 40C for NSW inland areas, meteorologist Jordan Notara told AAP.

Residents in far north NSW should brace themselves for temperatures above 45C on Monday.

“We’re not having any major changes in temperatures, unfortunately, generally over the whole state the severe heatwave is predominantly going to continue,” Mr Notara said on Sunday.

“Inland parts are seeing temperatures generally staying at 40C for the next seven-day forecast.”

Firefighters are keeping a close eye on bushfires across NSW with four regions – the Southern Ranges, Central Ranges, Greater Hunter and North Western- subject to total fire bans on Sunday.

Total fire bans will remain in place on Monday for the Southern Ranges, Central Ranges, Greater Hunter and Greater Sydney.

NSW Police has reminded motorists it’s not only an offence for children or pets to be left unattended in a vehicle, but it can be deadly.

Drivers are also reminded to keep an eye on elderly and disabled members of the community in cars during days of extreme heat.

“Everyone needs to take care in hot weather, but some people are at higher risk of heat illness, especially if they are older, live alone or are socially-isolated,” a police spokesman said.

The Australian Veterinary Association has warned farmers to take measures to protect livestock in the extreme heat.

AVA President Dr Paula Parker says livestock and horse owners should ensure water supply is high.