The Southern Highlands region of New South Wales is the latest to be severely impacted by heavy rain and flash flooding, with the Illawarra Highway currently closed by a sinkhole which has opened up beneath a stretch of road near the village of Burrawang, between Moss Vale and Robertson.

NSW Police posted this video just before midday on Tuesday alerting people to the dangerous situation.

The Illawarra Highway has been closed between Robertson and Moss Vale, due to a sinkhole at Burrawang.

Please defer any unnecessary travel and remember to never drive through flood waters.

Please check https://t.co/exN4TmYuvD for updates prior to travelling. pic.twitter.com/8dzS7VoZSr

— NSW Police Force (@nswpolice) March 8, 2022

The road is closed to traffic in both directions, and while diversions on minor roads are possible at this time, heavy vehicles are advised not to use the highway.

It's the latest major disruption to traffic in the Illawarra and Southern Highlands regions, which have received some of the heaviest rain in the state in the last 24-72 hours.

As we told you earlier today, the town of Mittagong, about 90 minutes southwest of central Sydney, received the heaviest rain in NSW in the 24 hours to 9am on Tuesday. It received 232mm, which is more than two months' worth of rain at this time of year.

Kiama, at the southern end of the Illawarra region has received 90 mm, 134.8 mm and 88.6 mm in the last three 24-hour periods, for a total of 313.4 mm across three days.

Already this year, Kiama has received 1053.5 mm in total. The bulk of that has fallen in the last two weeks, which is why the Princes Highway was closed by a landslide last week.

GERRINGONG TO KIAMA: Princes Hwy remains closed northbound btwn Rose Valley Rd & Kiama due to a landslide. Diversions from Batemans Bay: Kings Hwy to Hume Hwy at Goulburn. This route is suitable for all vehicles including B-doubles. Avoid the area, delay non-essential travel pic.twitter.com/SYQKhBb0Ck

— Live Traffic NSW (@LiveTrafficNSW) March 2, 2022

The situation in the southern half of NSW is expected to ease slowly from Wednesday, with showers becoming less heavy and more infrequent.

As things stand early on Tuesday afternoon as we write this story, the Southern Highlands and Illawarra are having a brief break from heavy rain, with the worst weather further north in the Sydney and Central Coast regions.

But heavy rain with the chance of flash flooding remains in the forecast for the rest of today.

Meanwhile the effects of Monday's Mittagong rain were captured by Weatherzone meteorologist and Southern Highlands local Jess Miskelly.

Tiny creeks became raging torrents and entire streets were awash – which is exceptionally unusual in a part of the world where the local geography is very different from the sort of low-lying floodplains we've seen flooded this week in places like Lismore and western Sydney.

As Sydney's Daily Telegraph reported, the town of Bowral, just over the hill from Mittagong, was cut in half by flash floods which surged over the bridges and blocked many crucial connective roads across the town.

"Long term residents are saying it's the worst flooding they've seen since the 1970s," Miskelly said.