More than 40 people have been rescued from floodwaters at two Cairns caravan parks as ex-cyclone Nora dropped 100mm worth of rain "in a minute". Desperate residents and visitors called state emergency services workers for help on Monday night as flash flooding swamped the parks on Cairns' outskirts. Queensland Fire and Emergency Services (QFES) Far North Regional Operations Director Lance Duncan said while authorities had braced for rain, the strength of the downpour had been unexpected. "We weren't prepared for 100mm of rain in a minute," Mr Duncan said. Emergency crews are currently working to rescue a person trapped by floodwaters on the Captain Cook highway, north of Cairns. The region is bracing for major flooding with the Barron River expected to reach its highest level in a decade, while Townsville has also been told to prepare for heavy falls as the weather system moves south. Cairns remains cut off by flooding to the north and south, with both the Bruce Highway and Captain Cook Highway closed in parts. All up, 42 people had to be rescued from the Big4 Crystal Cascades and the Coolwaters Holliday Park on Monday night, with three people taken to hospital with minor injuries. "They've gone through a devastating ordeal," he said. "They've lost a lot of their caravans, their vehicles... All of their livelihood, their clothing, all their personal belongings would be damaged." A Big4 Caravan Park Crystal Cascades spokeswoman said they were assessing the damage and cleaning up after cars and campervans smashed into buildings. "Everyone is safe," she told AAP. Two people were also rescued from their vehicle near the Captain Cook Highway. A Bureau of Meteorology spokesman said the far north has received extraordinary rainfalls, with potential for further downpours and thunderstorms throughout Tuesday. Port Douglas was hit with nearly 600mm of rain in the 24 hours to Monday morning, while Kuranda, just north of Cairns, had more than 400mm with nearby Barron Falls raging with water. Cairns council has warned residents that major flood levels are occurring on the Barron River at Caravonica, Kamerunga and Lake Placid. "Properties in this area may experience flooding as a result of heavy rainfall overnight combined with a high tide this morning," the warning said. The council has urged residents to get ready for flooding, and again warned motorists not to drive through roads covered by water. Authorities have been forced to close 15 schools and 9 childcare centres in Gulf communities affected by Nora, and in and around Cairns. Port Douglas residents have also been told the town's water supply is at critical levels as the local water treatment plan is struggling to cope with the continued rain.