Drink plenty of water, eat cold foods like salads and fruit, take a cool shower or bath if overheated, and limit or avoid consuming dehydrating alcohol and caffeine.
A list of "simple precautions" to prevent heat-related stress and illness are being offered up by the Royal Flying Doctor Service (RFDS) South Eastern Section as summer 2020 begins.
The RFDS is reacting to a forecast of "hotter than average day and overnight temperatures" this summer.
Extreme heat, or heatwave conditions, can affect a person's health quickly and unexpectedly, it says.
The RFDS reports heat-related stress is a dangerous medical condition and can develop into a life-threatening illness if not caught early.
Many Australians suffer heat-related stress and illness every year, it says.
RFDS chief medical officer, Dubbo's Dr Randall Greenberg, is urging care of the young and old.
"It's important to look out for symptoms in infants and young children including headaches, dizziness, faintness, nausea and vomiting, irritability, restlessness and a reduced number of wet nappies," he said.
"While anyone can be affected by heat, some members of our community are more vulnerable than others.
"Older people, and those taking certain medicines, may not be able to cool down in the hot weather."
Dr Greenberg said the best way to prevent heat stress was to drink plenty of water and stay as cool as possible.
"Keep your water bottle with you and keep out of the sun in the hottest part of the day," he said.
The list of "simple precautions" also includes staying indoors if possible between 11am and 3pm, and seeking shade when outside.
Making use of fans or air conditioners and getting enough sleep are also on the list.
The RFDS is encouraging the wearing of lightweight clothing, a hat and sunglasses, and application of SPF 50 sunscreen when heading outside.
"Checking on others", including children, the elderly, pregnant women, people with medical conditions and pets, is also advised.
"Importantly, if you become very unwell, contact your GP or go to the nearest hospital emergency department," Dr Greenberg said.
"If symptoms are serious, call triple zero for an ambulance immediately."
Summer got off to a hot start in Dubbo with 42.8 degrees Celsius recorded on December 1 and 36.3 degrees on December 4.
But largely below-average maximum temperatures have followed.
The average top temperature in the city during December is 31.6 degrees.