NSW Health has issued an air pollution alert as the Shoalhaven prepares to swelter through another summer heat wave.
They have warned of an increased level of ozone in the atmosphere likely to affect residents with respiratory problems.
Sydney's air quality is forecast to be poor on Tuesday, when the mercury is expected to hit a top of 32 in Nowra and 37 degrees in the west.
"Those with respiratory diseases such as asthma should follow their action plan and use their relieving medication where necessary,” a NSW Health alert states.
“If respiratory symptoms worsen, they should seek medical advice.”
Temperatures will dip to 25 degrees on Thursday before rising to 36 degrees on Friday.
The situation gets worse heading out to rural areas and NSW residents have been warned to brace for an extended period of scorching weather as a hot air mass settles over the state.
According to the NSW Office of Environment and Heritage ozone forms in the lower levels of the atmosphere on sunny days by chemical reactions between reactive organic gases and oxides of nitrogen.
Ozone forms more readily in summer and reaches its highest concentrations in the afternoon or early evening.
NSW Health said ozone can cause eye, nose, throat and lung irritations, coughing and shortness of breath, and may worsen chronic respiratory diseases such as asthma.