The deaths of five people have served as a tragic reminder of the danger of crossing flooded roads as Queensland was battered by storms.

A low swept across the southeast on Friday afternoon, and the relentless downpour cut off roads, washed away cars and left dozens stranded.

Motorists were gridlocked in peak-hour traffic and the rain wreaked havoc with public transport. Caboolture, north of Brisbane, was the hardest hit when more than 350mm of rain fell within 24 hours.

Some drivers tried to cross flooded roads, defying repeated warnings from authorities.

Advertisement

Two 4WD vehicles were swept into a torrent during an attempt to cross a road at Caboolture, which had been covered by the swollen King John Creek.

Three family members in one car drowned - a 74-year-old man, 39-year-old woman and a boy, 5.

A 21-year-old woman and her 16-year-old brother escaped from another car but 12 hours later, the body of their father was recovered 100m downstream.

In nearby Burpengary, firefighters rescued a woman who was clinging to a tree after she and her 75-year-old husband drove into floodwaters. His body was found more than six hours later.

An investigation was under way into each incident, Inspector Lee Jeffries said.

"I haven't seen anything as significant and as tragic as this."

Moreton Bay mayor Allan Sutherland said the SES was stretched to the limit and more than 200 roads had been closed.

For five hours at the height of the system, emergency services received more than 4000 triple-zero calls - 13 a minute.

Advertisement

There were nearly 246 swift-water rescue incidents and 58 rescues were performed. But it was not fair that emergency service personnel were being forced to risk their own safety to rescue residents who ignored warnings, Emergency Services Minister Jo-Ann Miller said.

- AAP