AN emergency alert has been issued for flash flooding in Forest Hill where 200 people have been evacuated.

"Forest Hill is likely to experience rapidly rising water levels and property inundation, posing an immediate danger to residents," the alert says.

"You should warn neighbours, secure your belongings and evacuate to the School of Arts Hall, Railway St, Forest Hill."

Residents in low lying areas of the Lockyer and Brisbane Valleys are being urged to leave their homes as more heavy storms sweep the area.

Weather bureau forecaster Ben Annells says that while the rain has eased around Toowoomba and Gatton, storms are still dumping up to 70mm an hour in some places further east.

"Since 9am (AEST) yesterday, Mount Glorious near Wivenhoe Dam has had 233mm and recorded in excess of 80mm in the hour to 8.30 this morning," he told AAP.

"Our heaviest hourly falls have been 94mm at Savages Crossing just south of the Wivenhoe Dam, but in the Lockyer Valley itself the focus is starting to shift a little bit further to the east but we're still seeing falls around 50mm to 70mm an hour in the Gatton and Laidley area."

Mr Annells said a heavy band of rain and storms extends from the Sunshine Coast to the northern areas of Brisbane, then sweeps west to the Wivenhoe Dam and down to Ipswich and the Lockyer Valley.

"There's some peripheral rain associated with that but the heaviest activity, which is what we're particularly warning for, is associated in that main band of storms.

"When you look at the fact that it's sitting there for a few hours, and if you're getting rainfall between 60 and 100mm an hour, you're obviously going to be getting falls of 150mm or even more than that so this is certainly going to produce problems.

"But it has moved a little further east and the floodwaters are moving down towards the Ipswich region today, eventually linking up with the Brisbane River.

"So rainfall that's occurring right over Ipswich at the moment is obviously going to add to that and that's what the severe weather warning is for."

Originally published as Flash flood alert for Forest Hill