A SUPER storm is brewing that could bring destructive winds, hail and flash flooding to Toowoomba, a weather group is warning.

South Brisbane Storms is warning people in south-east Queensland and particularly the Darling Downs areas to prepare for "one of the biggest storms" this year.

And its due tomorrow.

The group warned of "supercell thunderstorms capable of very large hail, a risk along with flash flooding and potential for damaging or even destructive wind gusts" which it said were at least a medium, if not high risk.

Its forecasters say the storm with stretch from Dalby to Brisbane.

The storm's severity will depend on the strength, timing and movement of a forecast southerly wind change.

The storm will develop just south of the New South Wales border and move northwards.

The perfect mix of five factors could produce a severe storm; a surface trough, a sharp upper trough, a jet stream exit region and possibly the added influence of the afternoon sea breeze, according to the group.

Those conditions could create a rotating thunderstorm with its own engine.

"It's these type of storms that can become capable of producing hail... possibly very large hail large enough to damage property and cars."

The Bureau of Meteorology is also warning of wild weather.

Forecaster Adam Blazak said Toowoomba was in the firing line today as was Warwick, Goondiwindi and Stanthorpe.

Tomorrow the storms could push further north and the storms could stay over the eastern Darling Downs on Saturday.

Mr Blazak said there were complicating factors affecting the forecast.

He said with a southerly change pushing in, variations in timing - even one hour - could mean the difference between storms and blue skies.

Toowoomba has copped the brunt of massive storms including this one photographed by Grant Rolph. It shows bolts striking a farmhouse just south of the corner of Hodgson Vale Rd and Meyninks Rd. Grant Rolph Photography

He warned of strong winds today and tomorrow.

Gusty but short-lived strong wind bursts could push over backyard furniture.

Mr Blazak advised residents to move loose items indoors.

"If you see dark clouds heading your way, the best place to be is inside," he said.

The bureau issues storm warnings at bom.gov.au/qld/warnings.

>> WATCH HAIL STORM THAT BATTERED CITY