Weather: Severe thunderstorm warnings issued in Canterbury

Severe thunderstorm warnings have been issued in Canterbury with the risk of torrential rain, possible flash-flooding, large hail and small localised tornadoes.

A mixture of unstable conditions are creating scattered heavy showers and thunderstorms over parts of the South Island on Saturday.

MetService forecasts a moderate-to-high risk of thunderstorms in Canterbury, North Otago, eastern Central Otago, Dunedin, and inland Southland this afternoon and early evening.

"These thunderstorms will produce localised heavy rain of 10-20mm/h, and hail mainly in the 5-20mm diameter range. There is also a low risk of a small tornado and/or funnel cloud."

The greatest risk is in Canterbury, where a severe thunderstorm watch has been issued from 2pm until 7pm.

Three severe thunderstorm warnings have also been issued for the Ashburton, Timaru and Waimate areas.

These thunderstorms are expected to be accompanied by torrential rain and large hail.

"Torrential rain can cause surface and/or flash flooding about streams, gullies and urban areas, and make driving conditions extremely hazardous," MetService warned.

"Large hail can cause significant damage to crops, orchards, vines, glasshouses and vehicles, and make driving conditions hazardous."

How to stay safe:

The National Emergency Management Agency advises that as storms approach you should:

  • Take shelter, preferably indoors away from windows
  • Avoid sheltering under trees, if outside
  • Get back to land, if outdoors on the water
  • Move cars under cover or away from trees
  • Secure any loose objects around your property
  • Check that drains and gutters are clear
  • Be ready to slow down or stop, if driving.

During and after the storm, you should also:

  • Beware of fallen trees and power lines
  • Avoid streams and drains as you may be swept away in flash-flooding.