Huge hailstones have rained down on Timaru and there are warnings there could be a tornado as a severe thunderstorm makes its way over Canterbury.
Timaru residents have reported hailstones the size of golfballs have fallen in the town, covering the roads and causing damage to some buildings.
MetService has issued a severe thunderstorm warning for the area and has warned that it is moving towards the northeast, although it is expected to ease.
MetService said the storms are expected to be accompanied by large hailstones which can "cause significant damage to crops, orchards, vines, glasshouses and vehicles, and make driving conditions hazardous".
MetService has also warned that there is a chance of a small tornado in parts of the South Island this afternoon.
It said people should take shelter if severe weather approaches.
Earlier today MetService had said there was no tornado risk, but they said it was difficult to predict tornadoes in New Zealand compared to the United States, as tornadoes here were a lot smaller and wre less likely to appear on rain radars.
Fire and Emergency have had to respond to more than 30 call outs from the damaging hailstorm in Timaru and Ashburton.
A spokesperson said firefighters had been helping residents put tarpaulins on damaged structures.
The Timaru Savemart store lost 18 skylights as a result of golfball-sized hail pelting down on the building.
It comes two days after SaveMart's store in Christchurch lost part of its roof due to a tornado.
#Timaru's thunderstorm formed along a line of converging winds at the ground, which forced air upwards ⛈️— NIWA Weather (@NiwaWeather) November 20, 2019
The explosive development of cumulonimbus cloud was captured from space as it moves north toward #Ashburton. pic.twitter.com/SvjP1uwmro
Big hail outside my office in Timaru. pic.twitter.com/8i4g8PaBNw— Andrew Falloon MP (@andrewfalloon) November 19, 2019