Christchurch has been battered by wild weather which has lashed the South Island this afternoon.

Metservice has issued a severe thunderstorm warning for Christchurch city, Canterbury Plains, North Otago and Central Otago, with the storms expected to be accompanied by large hail, damaging wind gusts and even tornadoes.

A Fire and Emergency (Fenz) spokesman said they had responded to nearly 40 call-outs from midday today in the South Island.

Thirty of those were in Timaru, where hailstones as big as golf balls pelted the streets and thunderclaps echoed through the city.

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A Christchurch local told the Herald enormous hailstones were denting cars parked on the street.

A Metservice spokesperson said these thunderstorms could be incredibly damaging.

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

"Very strong wind gusts can break branches from trees, damage roofing, and make driving hazardous especially for high-sided vehicles and motorcycles.

"Tornadoes can blow out windows, lift roofs, break large branches off trees, generate dangerous flying debris and blow vehicles off the road."

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;

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• 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.

Parts of the South Island's east coast have already been battered with hail the size of golf balls and torrential downpours as a front moves north.