Sydney sweltered through a short heatwave today, with the temperature soaring past all forecasts and hitting 34 degrees in parts of the city.

It's only the 10th time that Sydney has reached 30 degrees on or before September 15 in 160 years of weather record keeping, four of which have occurred in the past decade.

Swimmers flock to the beach at Manly on the first 30-degree day of spring. Credit:Brook Mitchell

The temperature hit 33.3 degrees at Sydney Airport just after 1pm, while Observatory Hill recorded 31.8 degrees just before 2.30pm.

It was even warmer at Richmond, where it hit 34 degrees at 1.30pm, while Badgerys Creek, Bankstown and Camden all hit 32 degrees.