Temperatures are set to soar in New South Wales, while people in Victoria and South Australia brace for cyclone-strength winds on a day of expected wild weather in the country's south and east.

Total fire bans have been declared across several regions in NSW, with Extreme Fire Danger forecast for Greater Sydney, Greater Hunter, Illawarra/Shoalhaven and the Upper Central West Plains.

NSW RFS Commissioner Trent Curtin said high fire danger was anticipated across the day.

"Today we're going to see very high temperatures in the high 30s and possible low 40s across parts of NSW, combined with very strong winds that will be in the 40[kph] range, but gusting anywhere up to 60 and 80 kilometres across parts of those areas," he told ABC's News Breakfast.

"We'll see high fire danger across most

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