Sydney just had its equal hottest September day on record after the mercury soared 15ºC above average in parts of the city on Tuesday.

A wave of exceptionally hot air that is currently sweeping across southeastern Australia caused temperatures to rise rapidly across the Sydney Basin on Tuesday.

Image: Forecast maximum temperature on Tuesday, according to the ACCESS-C model.

On an average September day, Sydney would typically see maximum temperatures peaking around 20ºC. But by midday on Tuesday, the city’s Observatory Hill weather station had already climbed above 33ºC and at 1:55 pm local time it reached 34.6ºC.

Sydney's provisional maximum temperature of 34.6ºC on Tuesday was the city's equal highest September temperature on record, matching the same value from September 26, 1965. Data at Observatory Hill is available back to 1859.

While temperatures might still be climbing at the time this story was written, a few other weather stations across the Sydney Basin also broke records on Tuesday.

Sydney Airport had reached as high as 35.7ºC by 2:00 pm, beating its previous September record of 35.6ºC from 2000, with data available back to 1939.

Tuesday’s hot weather in Sydney is part of a broader early-season heatwave that has been breaking records in several states and territories over the last few days. Unfortunately, this intense early-season heat will linger over parts of eastern Australia on Wednesday and Thursday before things cool down.