Heavy rain in Australia's southeast triggered flash flooding and cut off entire towns on Wednesday, stranding some residents on the roofs of their homes, as authorities issued snap evacuation orders with rivers staying above danger levels.

Flash flooding on Australia’s southeast coast has killed two people and cut off towns, isolating tens of thousands of residents, as officials warned more downpours were expected over the next 24 hours.

Severe weather will be possible during the afternoon and evening on Tuesday, May 20, per the National Weather Service in Wilmington.

The Mid North Coast has been warned to prepare for “dangerous and life-threatening” weather conditions and flash flooding, as six-hourly rainfall totals between 100 and 150mm are predicted to hit parts of the region on Wednesday and Thursday.

Roads and railroads in Bourbon County have been damaged by the recent storm system that came through this weekend.

When out on an outdoor adventure, it's essential to know the signs of a potential flash flood, should you ever be stuck in one. Here is what you should do.