The Health Department is urging people to remain hydrated and keep cool as temperatures climb over the weekend.
Groups who are most at risk of heat-related illness include people older than 65, children under the age of two, pregnant or breastfeeding women, people with heart disease or high blood pressure and people on certain medication.
A department spokesman said higher temperatures sometimes made it hard for the body to cool itself.
“The body loses heat by sweating, but when temperatures are consistently high, sweating isn’t enough to cool down adequately,” he said.
Symptoms of heat stress include muscle cramps, weakness, red skin, nausea and headaches.
Effects of heat stress can build up over a number of days and worsen heart disease and other chronic problems.
People are advised to drink plenty of water, limit alcohol, reduce physical activity and stay indoors.
The department is also urging people to monitor chlorine levels in pools and spas to ensure they stay within safe limits during summer.
The Bureau of Meteorology has forecast a maximum of 38C today with the chance of isolated showers and thunderstorms.
On both Saturday and Sunday the forecast maximum is 41C.For health advice call Healthdirect Australia on 1800 022 222.
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