According to the Bureau of Meteorology, a hot airmass will be drawn across western and southern NSW at the end of the week and over the weekend, with much of the state expected to be exposed to heatwave conditions.

BOM meteorologist Melody Sturm said in the Illawarra, South Coast and Southern Highlands, temperatures are expected to rise later in the week, and peak on Sunday/Monday.

Read more: Mass surf rescue at Austinmer just the latest in our long, hot, homebound summer

"(From) Thursday onwards, we'll see a rise in temperatures, and especially on Sunday and Monday we'll see the highest temperatures for that area," she said on Wednesday.

"Bega (will be) the highest - we'll see it being 14-15 degrees above the average (maximum temperature for January for that area), and it'll actually be 42 degrees on Monday.

"Going further up the coast to the Illawarra, especially inland, we see places reaching 10-12 degrees above average.

"For example, Nowra, 11 degrees above average, and Sunday/Monday you'll see 39 degrees."

Meanwhile, large parts of the NSW coastline continue to be subject to hazardous surf warnings.

Affected areas now include the Byron Coast, Coffs Coast, Macquarie Coast, Hunter Coast, Sydney Coast, Illawarra Coast, Batemans Coast and Eden Coast.

The BOM has advised that people should consider staying out of the water and avoid walking near surf-exposed areas.

Rock fishers should avoid coastal rock platforms exposed to the ocean and seek a safe location that is sheltered from the surf.

"Along the NSW coast, we still have a hazardous surf warning out," Ms Sturm said on Wednesday.

"We're seeing waves over three metres high just off-shore, and closer to the coast (there's) a little less height on those waves, but they're still quite powerful.

"The swell and the surf could be dangerous and hazardous for coastal activities, especially if you're looking at rock fishing, swimming or boating, so keep an eye out for those conditions."

Ms Sturm said the hazardous surf warning will still be going on Thursday for the whole coastline of NSW, including the Illawarra coast.

"On Friday there is no hazardous surf warning for the Illawarra, but only for Mid North Coast and Northern Rivers coasts," she said.

"So the last day of the hazardous surf warning for the Illawarra will be tomorrow."

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