Cantabs warned of damaging hail

03:20, Feb 23 2014
Canterbury weather 23 February 2014
A double rainbow over Christchurch.
Canterbury weather 23 February 2014
Rainbow seen among ominous clouds over Christchurch.
Canterbury weather 23 February 2014
The sun comes out following a brief shower over Christchurch.
Canterbury weather 23 February 2014
The rainbow, as seen from Sumner.
Canterbury weather 23 February 2014
Fresh snow on the alps with bright sunshine and a fresh westerly wind. Shot from The Cairns golf course Lake Tekapo.
Canterbury weather 23 February 2014
A rainbow to the south of the city. Photo taken from the Leisure-Port at the airport.
Canterbury weather 23 February 2014
The rainbow over Christchurch.
Canterbury weather 23 February 2014
Storm clouds approach.
Canterbury weather 23 February 2014
Hail stone in Halswell.
Canterbury weather 23 February 2014
The storm approaches Redwood.
Canterbury weather 23 February 2014
Hail in Rolleston.
Canterbury weather 23 February 2014
The storm approaches Rolleston.
Canterbury weather 23 February 2014
The storm approaches Rolleston.
Canterbury weather 23 February 2014
Photo taken from Wakanui Beach.
Canterbury weather 23 February 2014
Photo taken from Wakanui Beach.
Canterbury weather 23 February 2014
Lightning seen during the storm.
Canterbury weather 23 February 2014
Trees damaged by the storm.
Canterbury weather 23 February 2014
A mini tornado seen from Amberley.
Canterbury weather 23 February 2014
The storm approaches Kaiapoi.
defcon 3
Tornado as seen from Waipara
Canterbury weather 23 February 2014
Hail collected in Amberley.
Canterbury weather 23 February 2014
A tornado seen in Amberley.

MetService has issued a severe thunderstorm warning for parts of Canterbury with some of the region set to be pelted with large, damaging hail and torrential rain. 

The weather forecaster said in a statement this afternoon that its radar had detected thunderstorms near the mouth of the Ashburton River about 3.15pm.

The severe thunderstorms were moving north east and were expected to bring "very heavy rain and large hail" to Ashburton, Selwyn and Christchurch.

"Very heavy rain can cause surface and/or flash flooding about streams, gullies and urban areas, and make driving conditions extremely hazardous," the statement said.

This morning, MetService forecaster John Crouch said parts of Canterbury could be affected by ''large, damaging hail and squally winds'' gusting up to 100 kmh.

Forecaster said some hail stones could be bigger than 2cm in diameter. It could cause damage to crops and make driving conditions dangerous, Crouch said.

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He advised people to move their vehicles undercover to avoid damage like broken windscreens.

People should to ''take care'' if they saw ''big, dark looking'' storm clouds approaching from the south or south-west. 

North Otago and Canterbury would likely be worst affected, Crouch said.

Hail could affect Christchurch from about 5pm. Damaging hail storms usually affected parts of Canterbury two or three times each summer. 

''An upper cold trough is expected to move across the South Island today making the atmosphere very unstable over southern New Zealand,'' MetService's website says. 

In December, Mid-Canterbury experienced hail stones up to 3cm in diameter that damaged crops and smashed windows in the Mayfield area.

The Ministry of Civil Defence and Emergency Management advises that as storms approach you should:

- Take shelter, preferably indoors away from windows;
- Avoid sheltering under trees, if outside;
- 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.

The Press