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Sydney weather: Heat, fire threats dominate until change brings cool relief

Peter Hannam
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Sydneysiders are in for another scorcher after enduring unusually mild overnight conditions not seen in December.

The Bureau of Meteorology is forecasting a top on Wednesday of 38 degrees, matching Tuesday's maximum of 37.8 degrees.

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Sydney to swelter through another stinker

Temperatures above 37 degrees are expected across the city again but there's respite on the way.

The Rural Fire Service has declared total fire bans for the Sydney metropolitan region including the Blue Mountains and the central coast, and the Illawarra/Shoalhaven district. Hot, dry north-westerly winds will raise the fire danger rating to "severe".

Fires were threatening homes near Cessnock as of Tuesday evening.

Sydney has only had three previous back-to-back days of 37.8 degrees or warmer weather, the most recent in November 2002, said Agata Imielska, senior climatologist at the bureau. The other two occasions fell in January – in 1946 and 1960.

Workers' productivity may also take a hit because of the exceptionally warm overnight conditions forecast.

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Through the night, the temperature in Sydney has remained above 27 degrees, with the coolest point so far coming at 6.34 am, with 27.1 degrees recorded at Observatory Hill, bureau data shows. The temperature has since climbed above 31 degrees.

Penrith residents fared better, with the mercury dipping to 21.8 degrees at 5.18 am, although temperatures have jumped to almost 34 degrees in the three hours since. 

Only a handful of monthly records are older than the 1868 record, with the bureau's data beginning in 1858.

Ms Imielska said she would be "putting up the summer tent" in her backyard in a bid to get some relief.

A warming climate means "progressively, these older temperature records are being broken", Ms Imielska said.

Not only are hot records falling at a much higher rate than cold-weather ones, the margins by which records are being eclipsed is also tending to widen, she said.

Tuesday's heat was widespread. Adelaide, Canberra and Melbourne all joined the Harbour City in topping 33 degrees, the first time that's happened in December since 1965, Weatherzone said.

"It's a very hot air mass," Jacob Cronje, a senior meteorologist at Weatherzone, said.

Relief on the way

Relief in the form of a cool change should start to arrive by 4pm to 5pm on Wednesday as fresh north-westerly winds start to turn into southerlies.

It will take a bit longer, perhaps until 5pm to 6pm, before the "true cooling gets going" for the city, Jordan Notara, a bureau forecaster, said. Winds could strengthen to 50 km/h or more along the coast.

Thursday may even feel chilly, with just 22 degrees tipped for the city, before the mercury climbs back to the low 30s by Saturday.

Fire crews may have a busy time before cooler conditions arrive.

The RFS issued an emergency fire warning on Tuesday afternoon for two fires burning near Cessnock in the Hunter Valley. That warning was later downgraded as fire crews totalling about 70 people gained the upper hand.

Water-bombing aircraft, including helicopters, were brought in to quell the flames as they neared homes at Abermain and Neath, and electricity was briefly cut to residents as flames neared powerlines.

Warm times

For Sydney, Tuesday's top was the city's warmest December day in 11 years.

With weak sea breezes, the maximum temperature was similar across the basin. Richmond's top of 39.6 degrees pipped Hornesby and Penrith to be the city's hottest.

December days of 35 degrees, or warmer temperatures, occur on average slightly less than once per year.

If Wednesday clears that mark, as the bureau predicts, this December will have clocked three such days in the first half of the month alone.

The last time there was such a trio of warm days in a December was in 2000, with the record number of five set in 1979, Acacia Pepler, a bureau climatologist, said.

With the lingering heat, the Bureau of Meteorology said the strip of coastal NSW will have a low-intensity heatwave for Tuesday to Thursday. (See chart below.)

Other districts with total fire bans on Wednesday are the state's upper central and lower central west plains regions.

Help for homeless

The City of Sydney, meanwhile, stepped up efforts to help people sleeping rough during the hot spell. It is working with NSW Family and Community Services and St Vincent's Homeless Health Services to ensure homeless people have access to water, temporary accommodation, health services, sunscreen and shade.

"City staff and specialist homelessness services are on patrol in the city, providing advice and support to rough sleepers," the city said.

"The city's community centres and libraries will also be open, providing a safe and comfortable space to escape the heat," the city said, adding that those with medical emergencies should ring 000.

With Georgina Mitchell, Kate Aubusson

Follow Peter Hannam on Twitter and Facebook.

Weatherzone is owned by Fairfax Media, publisher of this website.

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