Sydney has recorded its highest temperature since 1939, with Penrith in Sydney's west reaching 47.3 degrees Celsius today.
The temperature hit 47.3°C at Penrith just after 3:00pm (local time).
The Bureau of Meteorology confirmed the preliminary data, saying it was the highest temperature recorded by a weather station in the Sydney metropolitan area.
However, the NSW BOM tweeted just after 4.00pm that they had missed a temperature in the north-western Sydney suburb of Richmond, at a now closed recording station.
The 1939 high was 47.8°.
Andrew Haigh from BOM said there would be some heat relief on the coast with a weak south-easterly change forecast to come through later on Sunday.
"That may just trickle into the western suburbs this evening, however the west is still expected to remain very hot for the rest of the day," he said.
"Tomorrow will be another hot day in the west, a little bit less so than today in the east."
Total fire bans and severe fire danger warnings were issued by the NSW Rural Fire Service for the Hunter and Greater Sydney, with the bans continuing into the start of the working week.
Sydney's heatwave caused problems at the Sydney International tennis, with fifth seed Kristina Mladenovic retiring after being badly affected by the heat.
The competition was out at Sydney Olympic Park, which had a top recorded temperature of 44.5° just after 1.00pm.
Animals at Taronga Zoo on Sydney's north shore were fed a variety of iced foods to keep them cool.
People working for Mission Australia's homelessness transport service Missionbeat were moving some people to cooler locations.
"We're particularly concerned for the welfare of older people who might have pre-existing health conditions and long term rough sleepers," Missionbeat programme manager Shane Sturgiss said.
"If anyone is concerned for the wellbeing of someone who is homeless, we encourage them to give us a call."
The New South Wales Rural Fire Service (RFS) has declared total fire bans in the greater Sydney region, and the Hunter.
An Air Quality Forecast alert of poor for the Sydney region has been issued by the NSW Office of Environment and Heritage, as ozone levels are forecast to exceed national air quality standards.