A new bushfire emergency broke out late Saturday in the Southern Highlands, threatening towns and multimillion-dollar regional properties. RFS Deputy Commissioner Rob Rogers later said properties had been reported lost or impacted in the Batlow area south of Tumut, North Nowra and Bundanoon in the Southern Highlands. At the peak of Saturday's fire emergency, there were 148 fires burning across the state, including 13 at "emergency" level. It came as Prime Minister Scott Morrison announced the unprecedented deployment of the military across the fire grounds, records tumbled for Sydney's hottest temperature and towns along the South Coast were plunged into an eerie darkness.

About 3600 personnel had been deployed to fight the fires, with hundreds more on standby for the outbreak of any new blazes. Briefing the media on Saturday evening, Rural Fire Service Commissioner Shane Fitzsimmons said vital infrastructure in the state's south-east was under threat and weather conditions were likely to deteriorate further. Those fears were realised when a southerly change brought gusts of up to 128 kilometres per hour and at least one new fire near Shoalhaven. The Morton fire, which affected residents in Bundanoon, Avoca, Exeter, Fitzroy Falls and surrounds, likely erupted on Saturday night after the existing Currowan fire spotted across the Shoalhaven River as winds blew fires to the north. "This fire will be evolving throughout the night and is of concern to us," an RFS spokesman said.

Residents in Eden, Womboyn, Kiah and surrounds were also affected by the expanding Border fire in the Bega Valley. Additionally, one woman was injured and properties were flooded in Cooma in NSW's south after a 4.5 million litre water reservoir burst on Saturday night. There were also fears for the safety of firefighters, as a fire-generated thunderstorm erupted in the Snowy Monaro, of a similar kind to the fire "tornado" that overturned a 10-tonne truck and killed volunteer firefighter Samuel McPaul. A southerly change started to sweep along the fire ground later in the evening, hitting Nowra at about 7.30pm and due to hit Sydney nearer to 11pm. Early in the evening Premier Gladys Berejiklian warned the state was "in for a long night", with the southerly expected to bring wind speeds of 80 kilometres per hour or more.

Premier Gladys Berejiklian and Emergency Services Minister David Elliott on Saturday. Credit:AAP "We're in for a long night, I make no bones about that ... it's a very volatile situation," Ms Berejiklian said on Saturday. "Mid-40s temperatures plus wind gusts mean not only is the situation exacerbated but when the southerly does come in, it will exacerbate those conditions more." Mr Fitzsimmons said aircraft and ground crews are protecting major infrastructure and utilities, including the Snowy Hydro. "Fortunately at this stage I'm not getting reports of significant infrastructure damage, but I'd be surprised if we're not seeing reports of damaged infrastructure before the night is over," Mr Fitzsimmons said.

RFS tankers at Moruya on standby on Saturday. Credit:Kate Geraghty Of the greatest concern was infrastructure across the Southern slopes and ranges. "Not only have we got installations like the Snowy Hydro system, we've also got pretty significant industry-based infrastructure like saw mills and massive employment centres," Mr Fitzsimmons said. "We're shoring up critical infrastructure ahead of firefronts bearing down on them. "It's going to be a long and difficult few hours and a very dangerous few hours given the number of emergency alerts."

It comes after a historic announcement by the Prime Minister, who revealed the military would be deployed en masse to assist with the firefighting effort. In the unprecedented move, Mr Morrison announced up to 3000 reservists would be dispatched across four states, also committing $20 million for the lease of four fire-fighting aircraft. Mr Morrison also confirmed he had cancelled next week's official prime ministerial visit to India and Japan, but said he would attempt to reschedule the trip for the coming months. Defence brigadier Mick Garraway said the focus would be on identifying the people with the skills - such as engineering and logistical expertise - to assist the state services in the recovery effort. "That will be done over the coming months," he said.

It was also confirmed that defence bases from Queensland through to Adelaide would be made available to serve as temporary accomodation for people caught without a place to stay. Loading The announcement came as Sydney sweltered through what is believed to be its hottest day on record, with the mercury at Penrith soaring to 48.9 degrees. The Bureau of Meteorology is yet to verify it as a weather record, but records show the previous hottest temperature had been recorded as 47.8 degrees in 1939 at a now-defunct weather station in Richmond. Mr Fitzsimmons revealed authorities were now relying on modelling for the "worst case scenario" to predict the fire's spread, rather than the "most likely scenario", due to how the New Year's Eve inferno played out.

"Generally speaking, over the last five years or so, the 'most likely' generally correlates with what happens on the ground," he said. "What we saw on New Year's Eve was that a lot of these fires were actually working to the worst case scenario, which is not the normal experience we've seen." Thirty-one strike teams – made up of multiple trucks and personnel – were positioned at strategic locations throughout the state on Saturday. Crews from other states and overseas bolstered numbers, particularly Queensland, where eased conditions have freed up some resources. On Saturday morning, Mr Fitzsimmons confirmed a report by The Sydney Morning Herald that the federal government has failed to produce additional funding requested by the National Aerial Firefighting Centre, which oversees a fleet of 145 aircraft.

Loading Mr Fitzsimmons said the centre was yet to receive a "positive response", more than 18 months since it put a business case to the federal government for the additional funds to "shore up some additional capacity and certainty". It had asked for between $11 million and $12 million – to be matched by the states and territories – but had instead been given "one-off" cash injections over the last two fire seasons. "We haven't seen that business case adopted or locked in at this stage," Mr Fitzsimmons said. During a press conference later in the day, Mr Morrison said the federal government would agree to providing funding on an "ongoing" basis.