Sydney sweltered through its hottest early September day in 159 years on Wednesday as the temperature reached 33.8 degrees in the city at 2.30pm.
It was also the fourth-warmest reading for any September day.
A hot and windy day saw fire risks lifted to extreme in parts of Sydney and elsewhere in the state. The NSW Rural Fire Service said about 1000 firefighters were dispatched to fight 94 bush and grass fires that were burning around NSW. Thirty eight remain uncontained.
A bushfire emergency warning issued for Richmond Vale near Cessnock in the Hunter where a number of properties are under threat.
The RFS said the out of control fire had broken containment lines but firefighters and aircraft are working to protect properties and slow the spread of the fire.
The air tanker Thor was sent to assist and emergency alerts have been sent to people in the area.
The main route through Richmond Vale, Leggetts Drive, has been cut in both directions and residents have been advised to seek shelter and protect themselves.
A separate fire has broken out at Black Hill, east of Richmond Vale. The RFS has issued a watch and act warning for the fire which is burning close to the M1 motorway.
Firefighters are also monitoring the fire burning at Beacon Hill on Sydney's northern beaches.
A burst of early season summer-like weather has put emergency services on high alert with total fire bans declared for the greater Sydney and Hunter regions, the North Coast and the north-west.
The heat was fairly uniform across the basin, with most suburbs reaching at least 33 degrees. Sydney Airport hit 35.3 degrees and Bankstown 35 degrees.
The previous warmest temperature this early in the month for Sydney was 32.2 degrees on 13 September 2009, a level beaten by 1.6 degrees.
Other NSW sites setting early season records include Richmond, Williamtown, Scone and Port Macquarie, Blair Trewin, the bureau's senior climatologist, said
"Not only is it significant for September, it's even extreme [for so early in the month]," Brett Dutschke, a senior meteorologist with Weatherzone, said.
The earliest in September that Sydney has had a 33-degree day was 11 years ago, and 11 days later in the month on September 24, he said. The September average for daytime temperatures is 20.1 degrees.
"Parts of Sydney are likely to have fire danger ratings going into the extreme category today," Mr Dutschke said.
As of Wednesday morning, the RFS had reported 70 fires burning across the state with 20 of them yet to be contained. The service requests members of the public report any sightings of unattended fires immediately.
@ 8:30am there are over 70 fires burning across #NSW. 20 are yet to be contained. Check for fire near you. #NSWRFShttps://t.co/NpNcAUu0rjpic.twitter.com/2x7jzeQewL??? NSW RFS (@NSWRFS) September 12, 2017
The extreme fire conditions are a combination of the heat, wind and how dry the conditions have been in recent months.
Over the past 90 days, the city has had one of its two or three driest periods for this time of year, Mr Dutschke said.
"We're lucky today is not as windy as tomorrow," he said.
The strongest gusts in the Sydney region so far have been at places such as Camden with 74 km/h and Sydney Airport with 69 km/h.
Winds, though, will swing around to the south by the evening, sending temperatures back to about 20 degrees by 9pm on Wednesday.
By Thursday, though, the wind chill combined with cooler, dry air will make for a sharp return to wintry conditions, Mr Dutschke said. Gusts could reach 80km/h.
There is little sign of rain, other than the odd shower, for at least a week.
After the cooling off patch from Thursday, temperatures should climb back to mid-20s or higher by early next week.
The following weekend, though, should see a return to hotter conditions.
"It looks comparable to today at this early stage," Mr Dutschke said.
The record for any September day in Sydney is 34.6 degrees, set on the 26th of the month in 1965. The two other days hotter than Wednesday were the 34.5 degrees on 29 September 2000 - during the Olympic Games in Sydney - and the 34.2-degree reading on 25 September 1980.
September is typically a transition month as wintry cold fronts vie with bursts of heat drawn from Red Centre.
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