Heavy rains that brought flash flooding in southeast Queensland for the past 72 hours has turned its attention on the region's inland, soaking much of the area of Brisbane's north and towards Ipswich and Darling Downs, as road conditions on areas earlier hit by record rainfall were still considered dangerous by authorities.

State authorities said on Monday that flash flooding has rendered roads in southeast Queensland impassable as the Bureau of Meteorology maintained its severe warning alert for flash flooding from the Sunshine Coast to the fringes of New South Wales while surfing activities on the mentioned areas are still being discouraged due to the dangerous conditions.

While the general weather conditions have mostly improved, Bureau forecaster Bret Harrison cautioned that rainfall may not be as intense but we are still "expecting rain to continue and ease only slightly in the afternoon."

Mr Harrison said that roads would remain underwater until Tuesday and police issue warnings that plodding through floodwaters would be highly risky even for those motorists who are on SUVs.

Relentless rainfall poured more than 200 millimetres on the Gold and Sunshine Coasts while some 130 millimetres were dumped on the northern part of Brisbane as the weather system battered the areas overnight with heavy downpours and wind gusts of up to 80kmh.

Coastlines were eroded by more than a metre high as strong winds gusted through the beaches of Gold Coast, Brisbane and Cape Moreton where the wind picked up in gust of about 106kmh as waves reportedly reached nine metre high off the coast of South Stradbroke Island.

The fierce weather system felled a great number of power lines state-wide and up 20,000 homes and business establishments were left without power overnight by the disturbance, which prevented repair crews from reaching lines located in flood-stricken areas to restore power services.