Hail the size of tennis balls lashed an eastern coast city in Australia on Tuesday, reportedly smashing windows and damaging cars and buildings, as a severe storm swept through.

Reports said the storm shut down the city of Lismore for 15 minutes as huge hailstones rained down.

"There are reports of giant hail in parts of Lismore of up to five to six centimetres and we're really worried about the potential for these thunderstorms to continue for the rest of the afternoon," Michael Logan of the Bureau of Meteorology told state radio.

"These thunderstorms have the potential to be really quite frightening, with some really extreme weather associated with them."

State Emergency Services said it received scores of requests for help after the storm.

Weather experts said the temperature plummeted from 29 to 15 degrees Celsius within an hour as the storm swept in and warned that more thunderstorms could be on the way.

"A trough of low pressure is tapping into very warm, humid air and triggering severe thunderstorms," Matt Pearce of forecaster Weatherzone said.

"In addition to the warm, moist air at the surface, there is a layer of very cold air higher up. This is creating perfect conditions for giant hailstones to form."