NSW set for first heatwave of the season, Thursday to peak at 36 degrees in Parkes

NSW is set to get an early taste of summer, with record-breaking heat forecast for parts of the state later this week - prompting a warning from fire and health authorities.

Temperatures in Sydney are set to reach the mid- to high-30s on Thursday and Friday, and more than 40C in the far west.

Areas west of Wagga Wagga are predicted to cop it the worst in what the Bureau of Meteorology is tipping will be the first heatwave of the season.

Parkes is expected to reach 36 degrees on Thursday and 35 on Friday. Wednesday’s hot conditions peaked at 35 degrees.

"For some places it's looking fairly likely we will receive record temperatures for this time of year," the Bureau's Jake Phillips told reporters in Sydney on Wednesday.

Overnight temperatures are also expected to remain warm for a large part of the state, he said.

"It's going to feel pretty summery; it doesn't feel like spring anymore."

A high bushfire danger is likely in parts of the state, with the Rural Fire Service on alert.

Rural Fire Service Inspector Ben Sheppard said forested areas up and down the NSW coast will be closely monitored.

"As this is the first heatwave of the season we're encouraging people to check their property is prepared," he told AAP.

NSW Ambulance chief superintendent Alan Morrison urged people to take extra care and avoid the heat, especially children and the elderly.

"Heat can kill which is why it's so important to stay hydrated and look out for the elderly, the young and pets," he said in a statement.

Paramedics treated nearly 4500 people for dehydration between December 2017 and March 2018, and hundreds more for heat exhaustion.

Australian Associated Press