Sydneysiders face an extended period of hot weather with warm nights likely to give only limited relief from the daytime heat peaks.
Fire risks will also be on the rise.
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NSW heatwave: Temperatures expected to hit mid-40s
Heatwave conditions will spread across the state with temperatures set to rise to 45 degrees in northern NSW at times during the week.
Sea breezes should continue to spare the city from the worst of this week's maximum temperatures scorching western suburbs - and inland parts of the state - with the exception of Wednesday, Rob Sharpe, a meteorologist with Weatherzone, said.
"Wednesday is definitely going to be the hottest day, with a weak sea breeze coming in late," Mr Sharpe said. "It could even nudge 40 degrees in the city."
Monday's peak of just under 30 degrees has already been reached in the city, while inland sites such as Richmond exceeded 38 degrees.
Sydney's current forecasts from the Bureau of Meteorology are for tops in the city of 31 degrees on Tuesday, rising to 38 degrees on Wednesday.
In the west, the mercury is likely to climb into the mid to high 30s each day this week until Sunday, with Thursday offering the only day of relative relief with 30 degrees expected. Richmond and Penrith are both forecast to reach 40 on Wednesday and 42 on Friday.
Humidity will make the warmth feel particularly oppressive, with overnight temperates remaining high. For Sydney, the minimums should stay above 21 degrees, with Saturday morning not falling below 25.
![Beachy weather ahead for the next week or longer for much of NSW.](/web/20170111161246im_/http://www.smh.com.au/content/dam/images/g/t/9/a/1/p/image.related.articleLeadwide.620x349.gto2rw.png/1483945683390.jpg)
The warm nights are likely to last well into next week and beyond, possibly putting January records in play, Mr Sharpe said.
Sydney had its second hottest December on record for minimum temperatures, at 2.5 degrees above the norm, the bureau said. It capped a year that was the city's hottest on record for minimum, mean and maximum temperatures.
Severe heat risks
Across the state, the hottest day during the current heatwave is likely to be on Friday, when a large swathe of north-western NSW could climb above 45 degrees. (See bureau chart below.)
![](http://web.archive.org./web/20170111161246im_/http://www.smh.com.au/content/dam/images/g/t/o/4/f/e/image.imgtype.articleLeadwide.620x0.png)
"It will be one of the longest hot spells on record for northern NSW," Mr Sharpe said.
The Rural Fire Service has also stepped up warnings about the fire risk, especially for grass fires.
After a wet & warm 2016 current conditions pose real threat from grass fires. Now is the time to be prepared https://t.co/1cBsSmSHpv #NSWRFS pic.twitter.com/lNVpCdLy2M
— NSW RFS (@NSWRFS) January 8, 2017
"We're expecting severe heatwave conditions to spread across the north of NSW this week," said Simon Louis, a bureau forecaster.
"These heatwave conditions are being caused by a slow-moving weather pattern, associated with quite weak southerly changes which are not effectively clearing away the hot air as [its moves] through."
(See below for chart of the predicted heatwave for eastern Australia from Wednesday, including areas of "extreme" conditions in red.)
![](http://web.archive.org./web/20170111161246im_/http://www.smh.com.au/content/dam/images/g/t/o/8/4/e/image.imgtype.articleLeadwide.620x0.png)
RFS Commissioner Shane Fitzsimmons warned that high rainfall, combined with hot weather throughout 2016, has caused vegetation to grow longer and dry out.
Recent fires have burned through more than 5500 hectares with an estimated $650,000 in crop losses, 300 sheep killed and the destruction of fencing.
Mr Fitzsimmons has urged farmers to protect their properties by putting in firebreaks around paddocks and other valuable assets and warned motorists not to drive through or stop in long grass.
"Even if it's just for a few minutes - as the heat from a car's exhaust can be enough to start a fire," he said.
"Grassfires can move more than three times as fast as a bush fire. Act now, be prepared and survive."
With AAP
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