Smoke blanketed the region yet again on Thursday, perhaps worse than on any day of this year's bushfire crisis, with temperatures reaching 43.3C at Albion Park and 36C in Wollongong.

Air quality readings from the NSW Department of Planning, Industry and Environment showed Wollongong's air was remained "hazardous" for its levels of P2.5 particulate matter in the air.

And with fires closing the Hume Hwy and threatening Tahmoor and Bargo, the Illawarra is set for some nervous days ahead with another unpredictable windy scorcher forecast for Saturday.

The Maritime Union of Australia's assistant national Warren Smith said workers had been forced to stop because of the conditions.

"For the third day in two weeks, smoke has become so intolerable in Sydney that maritime workers have been forced to stop work," he said.

"Maritime workers in Newcastle and Port Kembla have also been forced to down tools due to the severe health risks and effects of working in such high levels of smoke."

No Port Kembla workers were stood down because of smoke on Thursday. The Mercury understands the day this happened was earlier in December. Some workers have also had heat conditions in their contracts kick in, which stopped work, he said.

"Its quite clear the combination's just disgusting - it's really bad for people," Mr Smith said.

While governments hold real-time data on particulate content in the air, it is only released as a rolling 24-hour average. The union wants this delay eliminated.

"It should be made public," Mr Smith said.

"There should be hourly counts so we can make decisions based on what's happening now, not last week, and workers can make decisions based on what's happening now."

Statewide, Rural Fire Service Shane Fitzsimmons said extreme fire dangers will start early in the morning and last all day, with winds making for "erratic and significant" risks.

Forecasts of a 30 per cent chance of rain for Sunday have now been revised , with Monday now the first day with any significant chance of rainfall. Rain is more likely on Tuesday, with a 50 per cent likelihood forecast by the Bureau of Meteorology.

Southerly winds are expected to help clear smoke but NSW Health is advising people to take care: stay hydrated, avoid alcohol, limit physical activity, and stay out of the sun.