Emergency crews are distributing sand bags after more than 140 millimetres of rain was dumped over parts of the Sunshine Coast north of Brisbane in just one hour.
A spokeswoman said heavy falls in areas between Caloundra and Noosa were causing problems, while on the north coast, more than 60 separate calls for help had been made from properties as far away as Bundaberg.
Black Pinch, north-west of Noosa, has received 138 millimetres in an hour, and over 400mm during the day.
Further inland, 125 millimetres has fallen at Cooran.
At Cooroy, 118 millimetres has been recorded.
Bureau of Meteorology (BoM) forecaster Tony Auden said the falls at Black Point were "phenomenal".
"It's nearly unheard of that that amount of rain would fall in this short time period in one location," Mr Auden said.
BoM has issued a severe weather warning for the region, with seas expected to reach five metres.
There have also been reports of localised flooding in Brisbane, on Beaudesert Road at Acacia Ridge, Milton Road in Auchenflower and on the Ipswich Motorway at Goodna.
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