29/12/2016 8:53 AM AEDT | Updated 29/12/2016 11:35 AM AEDT

NSW Weather: 'Extreme Heatwave Conditions' Tipped For East Coast

Authorities are warning residents to take precautions in extreme heat.

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Parts of NSW are set to sizzle on Thursday as a heatwave hits the state.

Large swathes of NSW are set to swelter through Thursday, with the mercury expected to hit 40C in many parts of the state as heatwave conditions grip the east coast.

Sydney city is forecast to hit a maximum of 37C while areas in the west of the city are predicted to be even hotter, according to the Bureau of Meteorology (BoM). Penrith is forecast to reach 41C, with Liverpool, Richmond and Parramatta also likely to nudge 40C.

Regional centres in NSW are also in for extreme heat, with Maitland in the Hunter region predicted to reach 41C, Tamworth 37C, Dubbo 39C and Grafton, 36C.

"We are looking at heatwave conditions," BoM senior meteorologist Claire Yeo told the ABC. "We will see those very hot, warm and humid conditions continuing right through to New Year's Day."

Police have also warned of "extreme heatwave conditions" in coming days, mainly in the north of NSW and especially over the north and mid-north coasts.

Temperatures in Sydney are forecast to stay above 30C through to the end of the month, BoM says.

BoM duty forecaster Simon Lewis said while the mercury was not expected to reach record highs on Thursday, there were still health risks.

"We have quite warm overnight minimums so people don't get a chance to recover in the overnight period from the build up of excess heat in the day," Lewis told the ABC.

Other capital cities are also in for a hot day, but nothing matching the heat expected in Sydney, with Melbourne expecting a maximum of 32C, Canberra 33C, Darwin 31C and Brisbane 30C.

Perth, Adelaide and Hobart are all looking at more moderate maximums in the mid 20s.

For those in parts of the nation impacted by extreme heat, authorities are advising people to stay well hydrated, avoid alcohol and sugary drinks and limit physical exertion.