New South Wales firefighters are bracing for catastrophic fire conditions across large parts of the state on Sunday as 21 fires remained uncontained. A statewide fire ban is in place for the entire weekend, with temperatures in some regional areas, including Scone in the upper Hunter region, north of Sydney, and Walgett in northern NSW, tipped to reach 46 and 47 degrees respectively. At 5am on Sunday, the NSW rural fire service advised there were 76 bush or grass fires burning across the state and 21 of those were not contained. The Bureau of Meteorology said a trough was moving northeast from the central region, producing very hot, dry and gusty northwesterly winds. “This will produce widespread severe to catastrophic fire conditions in central and northern districts,” the bureau said. Extreme fire danger ratings were in place for five areas in the state including the north coast, northern slopes, upper central west plains and lower central west plains regions. “To put it simply, they’re simply off the old conventional scale,” RFS commissioner Shane Fitzsimmons said on Saturday. Fitzsimmons said the severity of the conditions on Sunday could not be understated. He said conditions were worse than those on Black Saturday in 2009, which claimed 173 lives and has been described as one of Australia’s worst peacetime disasters. This will produce widespread severe to catastrophic fire conditions in central and northern districts Bureau of Meteorology Police pleaded with residents to heed warnings from authorities after three teenage bushwalkers were rescued from the Marramarra National Park on the Hawkesbury River, near Sydney. The two women and one man set off about 2.30pm on Saturday, carrying heavy backpacks, and quickly ran out of water. They called emergency services and were rescued after 6pm, suffering mild heat exposure and dehydration. The acting assistant commissioner Kyle Stewart said the actions of the trio jeopardised the safety of both themselves and first responders. “While the incident had a good outcome, it could have had a very different ending,” he said. “The simple message is stay out of the national parks and state forests and make sure you avoid any outdoor activities that will put you at risk.” The heatwave across south-east Australia continued to break records on Saturday. Parts of Western Sydney reached 47 degrees on Saturday afternoon, including Penrith, which experienced its hottest day on record. The outback town of White Cliffs, in NSW’s north-west, broke the record for the hottest minimum overnight temperature. Residents endured a stifling night with a low of only 34.2 degrees. South Australia’s northern regions and Queensland’s south were also caught in the heatwave. Canberra recorded its second consecutive 40 degree day for only the third time in its history, while Sydney’s Observatory Hill broke the record for the longest-running spell of days above 35 degrees, which now sits at 10. While regional areas in NSW were set to swelter again on Sunday, a cooler change was expected to blow into Sydney. Temperatures in the city were not forecast to rise above 30 degrees with a possible shower. Firefighters kept a close eye on a bushfire east of Dunedoo overnight and said they would take advantage of the milder morning conditions to undertake back burning operations.