Australia’s east coast was smashed by heavy rains on Saturday, sparking dangerous flash flooding that forced the evacuation of multiple regions as the fast-moving waters unmoored houses, engulfed roads, stranded towns and cut power lines.

In Sydney, the country’s biggest city, authorities pleaded for people to stay at home as a major dam overflowed and a mini-tornado tore through a western suburb.

Most of the coast of New South Wales (NSW) state, which is home to about a third of Australia’s 25 million people, has already seen March rainfall records broken and authorities warned the downpour was likely to continue for several days.

“I hate to say this again to all our citizens of the state, but it’s not going to be an easy week for us,” NSW Premier Gladys Berejiklian told a televised briefing. “The rain may not stop till Thursday or Friday.”

Officials had issued nine evacuation orders for about 15 areas by Saturday afternoon.

Warragamba Dam, a main water supply for Sydney, began overflowing on Saturday afternoon. Officials warned that the overflow would quickly add to swollen rivers, leading to flash flooding.

People were urged to stay at home and avoid any non-essential trips, with officials lambasting those who had needed help after venturing out into the stormy weather.

Emergency crews responded to about 4,000 calls for help over the past two days, including 500 direct flood rescues, a level NSW Emergency Services Minister David Elliott said was “just completely unacceptable”.

“The message is clear: do not walk through or drive through floodwaters, do not drive over water that is covering a road,” Elliott said.

The federal government said the extreme weather was affecting its COVID-19 vaccine delivery in Sydney and throughout the state, but said delays should last only a few days.

Australia plans to deliver the first vaccine doses to almost six million people over the next few weeks.