Floodwater risk warning after deluge during heatwave

Another day of rain and storms is bearing down on the not-so-sunny Sunshine State in a wet start to summer, with warnings of possible flash flooding.

More than 127mm of rain fell in Brisbane on Monday night, while other areas around the southeast received up to 100mm.

Hervey Bay in the Wide Bay region was battered by 120mm of rain overnight after severe storms struck Queensland's coast.

It follows a severe storm sweeping across parts of Ipswich, Somerset, Lockyer Valley, Brisbane City and Moreton Bay about 2am on Tuesday, bringing heavy rain and causing flooding.

Police have warned drivers to avoid Gympie Road as westbound lanes near Strathpine Road in Bald Hills are flooded.

Since midday on Monday, the State Emergency Service has received 78 calls for help, with the majority being for sandbags and tarping on the Fraser Coast, Sunshine Coast and Brisbane.

The agency said five of those had been since midnight in the Moreton Bay and Somerset region.

The Bureau of Meteorology said the wet weather leading up to the festive season was due to a low-pressure system off the central Queensland coast near Mackay and a coastal trough bringing moist and unstable conditions.

Areas from Mackay down to Brisbane are expected to receive the most rain on Tuesday, as thunderstorms and a widespread deluge strike the coast.

"There is a risk of severe thunderstorms bringing locally heavy falls that could lead to flash flooding between Yeppoon and Brisbane," meteorologist Angus Hines said.

Mr Hines said the ground in the state's southeast was saturated, which meant flash flooding and river flooding were likely with another downpour.

Flood warnings and watches are in place in the Wide Bay, Burnett and south coast catchments.

This includes a moderate flood warning for the Mary River downstream of Gympie and a minor flood warning for the Brisbane River to Wivenhoe Dam.

Meanwhile, an extreme and severe heatwave warning is in place for inland parts of Queensland including Mt Isa and Cloncurry.

Mt Isa is expected to reach 44C on Tuesday, Richmond could reach 42C and Urandangi may hit 46C.