A short-sharp barrage of rain and hail pummelled Invercargill today leaving the city looking like a scene from mid-winter.

Roads and buildings in the city were covered thickly by the summer hail and the Fire Service dealt with 38 call outs between 2pm and 3.20pm.

Most of the calls were in the first 30 minutes, Fire Service Southland area manager Brendan Nally said.

A huge amount of rain and hail fell in about 10-15 minutes with the hail causing flooding as it sat in gutters and spouting, he said.

"We had buildings flooding everywhere. Some were quite large commercial premises like the Countdown supermarket."

A woman whose power supply was affected had to be taken to hospital as she relied on it for medical support, but there were no reports of injuries.

"It was very impressive, and there was a lots of water, but it was not significantly dangerous," Mr Nally said.

There would be a few insurance claims for water damage.

The weather had since settled and the roads dried, he said.

"It was just like this bizarre event that just came and went - it went as quickly as it arrived. So everything's back to normal again."

The sky also lit up every few seconds with lightning, he said.

MetService spokesman Bob McDavitt said the storm hit Riverton, about 40km northwest of Invercargill, about 1.45pm and moved east across the city.

It would have taken about an hour to cross the city and about four hours to cross the land, peaking about 2pm, he told NZPA.

The brunt of the storm would have lasted about 10-15 minutes in each area as it passed over.

The MetService measure 5-8mm hail stones, and rain of 7.6mm per hour at Invercargill Airport.

The thunderstorm dropped the temperature from 15degC to 8degC, Mr McDavitt said.

About 1500 lightning strikes were recorded in the four hours it took the storm to pass, 500 of which would have been at sea.

The weakening storm was moving north and would likely bring rain and cooler temperatures to Canterbury.

It would be much weaker by the time it reached the North Island, Mr McDavitt said.

Dunedin Sergeant Chris George said it had been wet with surface flooding in the city this morning, but had dried up.