Queensland's tropical north coast could receive several hundred millimetres of rain this weekend, while other parts of the state will experience heatwave conditions, the Bureau of Meteorology (BOM) says.
Thunderstorms have also brought solid downpours across Ipswich, Brisbane and Caboolture on Saturday afternoon.
BOM hydrologist Andy Barnes said there was already a flood watch on river catchments between Cooktown and Ingham.
"That includes some catchments that had some pretty good rainfall, so with more rainfall we are expecting some pretty quick rises in rivers and there is the potential for flooding in those catchments as well," Mr Barnes said.
He said the amount of rain would depend on the development of a tropical low.
"We could be seeing totals in the order of several hundred millimetres in places but just trying to pick those fall zones can be a little bit tricky at this stage, but there is definitely potential for flooding across those northern tropical zones," he said.
Mr Barnes said there were also minor flood warnings in some southern catchments.
He said northern areas had already received decent rainfalls in recent weeks and would be more susceptible to flooding.
"Those river levels are already that little bit higher, so it is a higher base point so there is potential for them to get higher again this time around," he said.
Mr Barnes said the Daintree, Barron, Johnstone, Tully and Herbert Rivers, as well as the Baffle Creek catchments could all be affected.
BOM forecaster Matt Marshall said severe thunderstorms were possible into Saturday night.
"These storms will be driven by a south-easterly change moving up from New South Wales.
"It is what we call a triple-point set-up and you basically have these three air masses colliding and creating all the ingredients you need for severe thunderstorms.
"There will be severe heatwave conditions about areas of the north-west and low-intensity heat wave conditions develop about inland areas of South-East Queensland, areas of the Wide Bay and Burnett, around the Central Coast and central interior."
Mount Isa is forecast to hit a top of 41 degrees Celsius today, Sunday and Monday.
Bundaberg is expecting a high of 34C today, with Maryborough predicted to hit 35C and Rockhampton, Gayndah and Monto hitting 38C.ABC