Sydney will sweat through two more days of oppressive heat and increasing humidity, with the mercury not expected to drop to 20 degrees until Tuesday.
Friday and Saturday will see maximum temperatures of 35 and 28 respectively, according to the Bureau of Meteorology.
![Norm McIntyre, Jeff Hanley, John Waddington, Clem Kennedy and Darryl Silk try to keep cool at the Dawn Fraser Baths in ...](/web/20170324185032im_/http://www.smh.com.au/content/dam/images/g/t/j/k/o/0/image.related.articleLeadwide.620x349.gtjdkh.png/1483010147698.jpg)
Rob Sharpe, a meteorologist at Weatherzone, says the expected increase in humidity, which hovered at 30 per cent on Thursday, will reduce the relief promised by the slight drop in temperature.
"Tomorrow is going to be similar, but probably a little less hot because we've got more cloud cover," he said on Thursday.
![Swimmers at Mahon Pool, Maroubra, escape the heat on Thursday.](/web/20170324185032im_/http://www.smh.com.au/content/dam/images/g/t/j/a/d/4/image.related.articleLeadwide.620x349.gtjdkh.png/1483010147698.jpg)
"But many people's homes will be very hot tomorrow night because of the humidity, so sleeping will be difficult unless you've got an air-conditioner ... it'll feel stickier than it did today."
The heatwave is keeping Sydney on track for its hottest year on record.
Thursday marked the first day of the summer that a Sydney weather station recorded the mercury touching 40. While Tuesday saw a recorded high of 39, on Thursday parts of Sydney's west, including Penrith and Battery Creek, sweltered at 40 degrees.
"Holsworthy is very close [to 40]," Mr Sharpe said on Thursday afternoon. "So is Bankstown, Sydney Olympic Park; much of Sydney is very close to 40 degrees, except for places that have started to see the sea breeze come in."
![Mahon Pool provided relief for many Maroubra residents.](/web/20170324185032im_/http://www.smh.com.au/content/dam/images/g/t/j/a/d/5/image.related.articleLeadwide.620x349.gtjdkh.png/1483010147698.jpg)
The city reached a peak of 36.6 at 1:58pm before the breeze began dragging the temperature down.
Ben Domensino at Weatherzone reported that "the city has also experienced twice its usual amount of days above 35 degrees this year. The long-term average is three per year, although [Thursday] makes six so far in 2016 and [Friday] could be number seven."
The Bureau of Meteorology forecasts Friday's high at 35 degrees for the city, 38 for Parramatta and Campbelltown and 39 for Penrith and Liverpool, with a 5 per cent chance of rain. Cooler weather will not arrive until the new year, when a southerly change is expected.
Weatherzone is owned by Fairfax Media, the publisher of Sydney Morning Herald.