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An air pollution alert has been issued for Sydneysiders as much of NSW prepares to swelter through another scorching summer day.
NSW Health has warned that the high level of ozone in the atmosphere is likely to affect people with respiratory conditions.
Sydney is forecast to hit 31C on Tuesday, while residents in the west are expected to see the mercury rise to 37C.
Inland NSW will bear the brunt of the hot weather, with the heatwave expected to intensify to severe or extreme levels past 45C on Wednesday, the weather bureau says.
Sydney is also predicted to experience poor air quality on Wednesday.
Ozone pollution is caused by car exhaust and industrial fumes and gets worse on hot, still days.
Parents should limit the time their children with asthma play outside, NSW Health's Dr Ben Scalley says.
"Ozone levels reach their peak around 7pm in the evening and tend to be lowest in the morning, so it's best to plan outdoor play in the morning when the day is cooler," he said.
The NSW Rural Fire Service has warned of a heightened risk of bushfires this week, and urged farmers to protect their properties by putting in firebreaks around paddocks and other valuable assets.
The sweaty conditions are expected to ease on Thursday with a southeasterly pushing up the coast and temperatures dropping to 27C in Sydney and 30C out west.
The reprieve won't last long, however, and temperatures are forecast to climb again on Friday.