Giant hail, storms and a rain deluge are set to hit parts of the south-east with residents warned of flash flooding.
Severe thunderstorm warnings with destructive winds, "giant hail" and heavy rainfall have been issued for parts of western NSW, the ACT and Victoria's Mallee and East Gippsland regions on November 28.
The Bureau of Meteorology said storm activity was being generated by a surface trough and unstable air mass over inland NSW.
It comes after storms wreaked havoc in South Australia with thousands losing power early on November 28 and flights grounded at Adelaide airport.
South Australia SES received almost 200 calls for help between 6am and 9am mostly due to flooding.
Scotch College south of Adelaide recorded 45.8mm of rain in an hour and wind gusts of 72km/h were recorded at Adelaide airport.
Flood watch alerts and damaging winds
A severe weather warning is also in place for the NSW South Coast, parts of Illawarra and Snowy Mountains forecast districts for heavy rainfall potentially leading to flash flooding and damaging winds.
From early November 29 six-hourly rainfall totals of 50 to 100 mm are possible, with isolated totals of up to 150 mm according to the Bureau.
People in areas such as Batemans Bay, Bega, Eden, Moruya Heads, Narooma and Merimbula could be affected.
Parts of NSW are also on flood watch due to widespread rainfall expected along the coast south of Sydney and the inland Central West.
The SES urges people in warning areas to move vehicles under cover or away from trees, securing loose items outdoors and stay away from fallen power lines.
Keep up-to-date with weather warnings at bom.gov.au/australia/warnings