Hunter health officials are urging people to stay indoors ahead of today's heat wave.
Temperatures are expected to soar above 40 degrees.
Thousands of firefighters are on standby ahead of what has already been a tough week.
Public Health Physician Kate Hardie says people need to drink plenty of water and be prepared.
"So, if you can, plan your day around the heat and try to minimise your physical activities outdoors during the middle of the day and try to stay cool," she said.
"For those people who are in houses that are difficult to keep cool, perhaps consider spending some time in an air conditioned venue, like a shopping centre or a library."
Doctor Hardie is also urging people to keep an eye on family or friends who might be at risk.
"We'd like to encourage people to make contact with any vulnerable neighbours or relatives that they have, to check how they're doing," she said.
"Particularly, if you are living in an area where you are expecting several days in a row of high temperatures."
Meanwhile, pet owners are being urged to think about the effects the heat will have on their animals.
Upper Hunter veterinarian Rachel Nugent says pets will often bear the brunt of hot weather.
"They actually suffer more than humans do because animals are unable to sweat underneath their coats," she said.
"The only way they can cool down is by panting, and if they get too hot and overweight, pets are particularly prone to overheating.
"They will overheat really quite rapidly and get very sick indeed."
Ms Nugent says a hot day is the worst time for dogs to be riding on the back of utes.
"That's a bad idea in this really hot weather too," she said.
"Although they'll be getting that lovely breeze as you travel along, the metal tray will get very, very hot," she said.
"We do have dogs that have got quite serious burns in their pads on hot days like this, where the sun's heated up the pads so much it's burnt the dog's feet."
© ABC 2013
13:25 EDT After a fairly cloudy morning, Sydney's skies are clearing nicely for a starry but cool night for Carols at the Domain.