Sydney can expect another scorcher on Thursday, with temperatures again climbing just shy of the 40-degree mark in the western suburbs.
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The Bureau of Meteorology is predicting a top of 35 degrees but the mercury may rise further - as it did on Wednesday when the maximum hit 37.5 degrees - if the sea breeze turns to be later or weaker than expected.
Sydney Airport was the hottest place in the city on Wednesday, with the mercury reaching 40.3 degrees.
"A small delay in a sea breeze can make a significant difference," Peter Zmijewski, a senior forecaster at the bureau, said. Similarly more cloud cover could trim the temperature by a degree or two.
Thunderstorms are expected across the Sydney Basin on Thursday afternoon and evening as the heat builds up.
Parts of the state's north should again climb into the 40s, the bureau said.
Holidaymakers heading back to Sydney might want to consider an early start as conditions turn less favourable for the beach after Thursday.
Apart from the north-east corner of NSW, most of the state can expect "a showery, thundery and cloudy day" on Friday, Tristan Meyers, a meteorologist with Weatherzone, said.
Rainfall totals are tipped for Sydney to be as much as 6mm on Friday and possibly 15mm on Saturday.
Saturday morning may also include thundery conditions for Sydney as a moisture-laden change moves through, Mr Meyers said.
Conditions should then be mild for a few days before temperatures start to climb by early February, he said.
After a cool start to January, average maximums in Sydney are running almost one degree above normal for the month.
On current forecasts, it is likely the city will record its 49th consecutive month of warmer-than-average temperatures, according to bureau data.