The heat proved too much for many who sought refuge at Kambah Pool or stayed inside to turn on air-conditioning machines for the first time in months.

Those who travelled to south coast beaches experienced the worst of the heat, with temperatures reaching 41 degrees at Kiama.

Soaring temperatures and gusty winds raised the fire threat across southern NSW, with fire crews responding to an out-of-control grass fire south of Goulburn.

The fire caused traffic chaos for those seeking an early escape to Sydney for the weekend, with northbound traffic diverted through Goulburn.

Weatherzone meteorologist Guy Dixon said conditions made work much harder for firefighters across the state.

"In Goulburn, the temperatures warmed to 37.1 degrees but the most significant feature of the day was westerly and north-westerly wind gusts of up to 80 km/h that fanned the flames," he said.

"In Canberra, we reached 36.1 degrees in the city and again there were gusty conditions with 72km/h winds recorded at 1.10pm.

"The last time we had a day this hot was back on November 23 last year, when temperatures reached 39 degrees."

But Mr Dixon said the weekend was likely to bring relief to the territory with temperatures set to drop overnight.

"On Saturday we will see a maximum temperature of 25 degrees and a chance of a shower in the morning, although it would be very light and isolated, probably only a millimetre or two."

"Sunday will be another mild day with temperatures reaching around 24 degrees before they begin to warn on Monday, potentially rising to the 29 degree mark on Wednesday."

Friday's heatwave comes as government and University of NSW research warns the NSW region will experience more frequent and longer heatwaves in the future as the climate warms, with the worsening extremes dependent on whether carbon emissions continue to climb

The heatwave projections, released on Friday during what was expected to be Sydney's hottest three-day spell in November in almost eight decades, cover the period to 2030 and then out to 2070.

The shift towards hotter weather was already evident, with south-eastern NSW experiencing about 18 more heatwave days a year compared with the start of the 20th century, the Office of Environment and Heritage said.

The ACT Rural Fire Service has routinely warned ACT residents to prepare for a long and potentially dangerous bushfire season that may last into autumn.

The strongest El Nino weather pattern since 1997, which is expected to bring hotter, drier days and more powerful winds in November and December, means it is unlikely last year's mild fire season will be repeated

Chief Minister Andrew Barr stressed the importance of increasing public awareness and community engagement to work alongside emergency services.

The grass fire near Goulburn on Friday afternoon destroyed close to 20 hectares of land on a property near Garroorigang Road.

Despite earlier hopes it would be kept at bay, the blaze came within 20 metres of a historic homestead at the South Hill property.

Multiple fire crews were working up and down the south and northbound lanes of the Hume Highway, damping hot spots.

- with Peter Hannam