SYDNEY'S record was officially broken when the mercury hit 47.3 degrees in Penrith on Sunday afternoon, making it the hottest day in the city's 158 years of recorded history.

According to the NSW Bureau of Meteorology (BoM), Penrith beat Sydney's previous record of 47 degrees, which was recorded in Richmond on February 11, 2017, at 3.25pm today.

But Nine News reported that the temperature may have reached as high at 48 degrees in Cambelltown, according to an electronic thermometer outside Campbelltown Performing Arts High School this afternoon.

It was a scorcher right across the city, with temperatures soaring to 46.3 degrees in Richmond, 45.1 in Horsley Park, 44.8 in Holsworthy and 44.5 in Sydney Olympic Park, while the CBD reached a high of 43.4 degrees just after 1pm.

A total fire ban was issued for the Greater Sydney and Hunter regions, as much of the country struggled through the record heatwave.

The NSW Office of Environment and Heritage also warned of higher than normal ozone levels, issuing an Air Quality Forecast alert of poor.

The BoM also issued a thunderstorm warning, with damaging wind gusts of over 90km/h headed for the ACT and western NSW.

SYDNEY'S record was officially broken when the mercury hit 47.3 degrees in Penrith on Sunday afternoon, making it the hottest day in the city's 158 years of recorded history.

According to the NSW Bureau of Meteorology (BoM), Penrith beat Sydney's previous record of 47 degrees, which was recorded in Richmond on February 11, 2017, at 3.25pm today.

But Nine News reported that the temperature may have reached as high at 48 degrees in Cambelltown, according to an electronic thermometer outside Campbelltown Performing Arts High School this afternoon.

It was a scorcher right across the city, with temperatures soaring to 46.3 degrees in Richmond, 45.1 in Horsley Park, 44.8 in Holsworthy and 44.5 in Sydney Olympic Park, while the CBD reached a high of 43.4 degrees just after 1pm.

A total fire ban was issued for the Greater Sydney and Hunter regions, as much of the country struggled through the record heatwave.

The NSW Office of Environment and Heritage also warned of higher than normal ozone levels, issuing an Air Quality Forecast alert of poor.

The BoM also issued a thunderstorm warning, with damaging wind gusts of over 90km/h headed for the ACT and western NSW.