Sydney weather: Thunderstorms and hail roll in after a day of extreme heat, with temperatures topping 40C

Parts of the east coast have sweltered through heatwave temperatures above 40 degrees as strong winds continue to cause chaos over a storm-ridden summer.

Scorching conditions swept across Australia during the long weekend moving from South Australia and Victoria to NSW on Tuesday morning, with much of the state - including Sydney - recording temperatures in the high 30s or low 40s.

Sydney Airport recorded a high of 43C while Penrith, Bankstown and Badgerys Creek also topped 40 degrees.

Temperatures were in the high 30s for much of the Illawarra region with Nowra and Kiama reaching 39 degrees.

Meteorologist Edward Townsend-Medlock said the heatwaves in the coastal areas were not as high as predicted due to an earlier-than-expected afternoon storm.

“The lovely change that came through today came a little bit earlier than expected, stopping coastal areas from reaching their maximum forecast of 40 degrees,” he told AAP.

Temperatures dropped quickly on Tuesday afternoon, with Sydney Olympic Park falling from 41 to 29 degrees in less than an hour.

“So in around two hours, temperatures have dropped around 10 to 15 degrees around the place,” Mr Townsend-Medlock said.

The cool change was a result of a severe storm moving up from the South Coast, likely to bring heavy wind, hail and lightning across Sydney and surrounding areas.

A severe thunderstorm warning is in place for Gosford, Sydney, Penrith, Parramatta, Woy Woy and Kulnura.

Winds began sweeping through Sydney’s CBD around 3pm while hailstones fell in north Sydney just before 4pm.

“Once we’re in this new cooler air mass, those storms should subside,” Mr Townsend-Medlock said.

That follows similarly strong storms on Monday night, which resulted in 211 call-outs for the NSW State Emergency Service, the majority in metropolitan Sydney.

The Australian Energy Market Operator has issued its lowest-tier warning for power supplies in NSW on Tuesday afternoon, encouraging industry participants to lift their output to meet expected demand.

Parts of north Queensland are also expected to be hammered by rain on Tuesday resulting in the highest totals of the summer season.

Severe weather warnings were issued by the Bureau of Meteorology for parts of the North Tropical Coast and Herbert and Lower Burdekin regions.

Rainfall totals between 100mm-200mm are forecast between Gordonvale south of Cairns and Rollingstone, north of Townsville, with some isolated areas set to be saturated by nearly 300mm of rain.

“We’re expecting widespread daily totals in the 100mm to 200mm (range) over the next 24 hours, and isolated totals in the 200mm to 300mm possible, as well as flood watches and a few minor flood warnings current for that region as well,” Senior Meteorologist Pieter Claassen told AAP.

“This will be the wettest events forecast so far this summer.”

The Bureau is also monitoring a seven-day cyclone risk from the Indian Ocean to the Gulf of Carpentaria and into the Coral Sea.

The Bureau said a tropical low in the Coral Sea has a 25-30 per cent chance of forming into a cyclone over the weekend and into next week.

“It is likely, depending on where it moves to and forms, it may increase rainfall over parts of far northern Queensland particularly if it moves close to the coastline,” he said.

Large parts of Queensland, including the northwest, central west and channel country, reached temperatures in the low-mid 40s on Tuesday.

Some towns in the WA’s Pilbara, Gascoyne and north interior regions reached 46C on Tuesday.

The NT interior also had a sweaty Tuesday, including in Alice Springs where temperatures soared to 43C.