Parts of Sydney have sweltered through 40-plus temperatures before the summer’s first southerly buster brought much-needed relief to the city.

Sydney’s CBD hit 32.1 degrees just after 3pm on Tuesday, while temperatures climbed to 41.6 in Penrith and 41.7 in Richmond. It was hotter in western Sydney than towns in regional NSW, including Bourke, where the mercury reached 40.4 degrees.

The dew point, which is the best measure of how sweaty you’ll be, tipped 21 degrees in the city and western suburbs – a rating the Bureau of Meteorology describes as muggy and uncomfortable.

Sydneysiders flocked to the city’s waterways and pools before the cool change forced down temperatures in some suburbs by almost 10 degrees in the hour after 5pm.

Tuesday’s scorcher came after days of hot weather across much of the country caused by a high-pressure system over central Australia.

NSW Ambulance had urged those over 60, tradies and parents with babies to be on the lookout for heat stress symptoms.

“Dehydration is the biggest thing that we do respond to, so drink lots of water,” acting superintendent Christie Marks told Nine News.

The BoM predicts the rest of the week will be mild, with temperatures staying around the mid-20s in Sydney on Wednesday and Thursday before rising slightly on Friday ahead of another hot Saturday.