People living in western and southern parts of inland New South Wales are being warned to prepared for a heatwave over the next week.
Residents of Broken Hill are expected to face top temperatures of at least 40 degrees for the next seven days, with a high of 44 degrees predicted for Saturday.
The Far West Local Health District population health director Therese Jones says elderly people, babies, children, people with a medical condition and people who live alone are the most vulnerable.
She is urging people to take the risk of heat-related illness seriously.
"Drink plenty of fluid, consider other people who might be vulnerable and may not be able to look after themselves, stay in air-conditioning if they've got it, cool off in other ways like sponging down, going to an air-conditioned place," she said.
The heat will also be felt in the state's Riverina region, with a forecast high of 45 degrees in Hay on Saturday.
Assistant Rural Fire Service (RFS) Commissioner Rob Rogers says people need to be prepared.
"People living in western New South Wales and down the south, they're certainly going to find really, really warm days," he said.
"They're to the point where it's so hot, it doesn't need a lot of wind.
"Speaking to the Bureau, they don't have any rain coming in the next week or so, just some isolated showers but no sustained rain."
There is a total fire ban in place for the southern Riverina.
Sydney is set to miss the worst of the heat although temperatures are predicted to creep up to 40 degrees in the city's west on Tuesday.
Today's forecast highs are 27 degrees in the city and 35 degrees at Penrith.
Signs of health-related illness include confusion, dizziness, fainting, nausea, vomiting, weakness, headaches and loss of sweating.
© ABC 2013
14:24 EDT Thunderstorms are due to develop daily across New South Wales and Queensland for almost two weeks.