The Bureau of Meteorology (BoM) has issued a severe weather warning for the entire area of NSW from the Blue Mountains in the west, to Newcastle in the North and Kiama in the south.
The storm started in the west and is quickly moved east towards the coast bringing hailstones, heavy rain and strong winds.
Heavy rainfall may lead to flash flooding, the BoM said.
The warning also includes Cessnock, Greater Newcastle and Wollondilly and Wingecarribee areas. Power outages have already been reported on the Central Coast at Avoca Beach, Copacabana, Davistown and surrounding suburbs.
A more general severe thunderstorm warning is also in place for the Hunter, Metropolitan, Illawarra, South Coast, Central Tablelands, Southern Tablelands, Central West Slopes and Plains.
The warning also included parts of the Mid North Coast, North West Slopes and Plains, South West Slopes, Lower Western, Upper Western and Snowy Mountains districts.
Eastern Australia has experienced a humid and stormy start to 2021 with daily widespread showers and storms (including several severe storms with hail and heavy rainfall) across Queensland, New South Wales, Victoria and South Australia since Thursday 31 December.
Storms are expected to contract to just New South Wales and Queensland from today.
On Saturday, severe thunderstorms saw rain rates at Warrnambool reached a one-in-50-year intensity with 30 mm falling in 12 minutes. Elsewhere hail was reported at Broken Hill, NSW and 27 mm rainfall fell over 15 minutes at Parkes.
Some other high total rainfall observed by BoM in the 24 hours to Sunday 9am AEST include:
• 53 mm at Warrnambool, Vic
• 61.6 mm at Okeh in NSW’s Northwest
• 51 mm at Parkes, NSW and 85 knot wind gusts recorded with the severe storm