Isolated thunderstorms could produce up to 100mm of rain overnight in south-east Queensland, the Bureau of Meteorology says.
Forecaster Sam Campbell said the heaviest falls could occur anywhere from as far west as Roma to as north as Rockhampton, depending on where isolated thunderstorms develop.
"Since 9am we've seen steady rainfall over most of south-east Queensland... generally widespread falls of 5-15mm," Mr Campbell said.
"They are expected to increase overnight with widespread falls of 20-50mm expected and possibly falls of up to 100mm."
The heaviest falls in the 24 hours to 9am this morning occurred inland of Mackay, where 162mm of rain was recorded.
The interior of the state has received between 30-50mm of rain.
Charleville in the state's west received 52mm in the 24 hours to 9am today, breaking the record for August rainfall that has stood for a century.
"We have a significant upper level low and associated surface trough lying around the interior of the state. They've been combined to introduce widespread rain, scatters showers and some isolated thunderstorms as well," Mr Campbell said.
"Generally, August is a very dry month for most of Queensland so it's unusual to see this much rain.
"Probably not since 2010 have we seen such widespread areas of the 30-50mm ranges we've seen so far."
The rain was expected to clear on Sunday morning for the south-east, while the southern inland region can expect some shower activity.
© ABC 2014
12:48 EDT Weather models are now showing an El Nino is unlikely to develop this year.