Fire crews remain cautious in Canterbury

Just one fire crew remains on the ground today monitoring the site of fires that have devastated parts of Canterbury.

But with tinder-dry conditions the situation was far from being treated as over, Fire Service spokesman Brent Dunn said.

Firefighters have left the site of a scrub fire which at one point spread over some 100 hectares near West Melton, and a fire at Mcleans Island last night has also been extinguished.

The site of Thursday's major blaze between Rolleston and Prebbleton now appears to be out, but one fire crew remains on-scene in case of any further flare-ups.

"We're on an enhanced response to any vegetation fires in Canterbury for quite a while," Mr Dunn said.

"Conditions are still tinder-dry. It's just going to take the wind to whip up and we'll probably be dealing with the same sort of thing again. But hopefully people have seen the news and will be a little bit more careful about what they do."

A blaze that burned through 2 hectares of bushland near Christchurch Airport late last night is being investigated after fears it was deliberately lit.

It took up to 50 firefighters to bring the fire under control by 11.45pm.

Temperatures around Canterbury were expected to rise above the mid-20s today, with Timaru expected to be one of the hottest areas with a top of 30C.

It was earlier feared that "dry thunderstorms" could spark more fires in the region today.

MetService forecaster Allister Gorman said the West Coast had been pounded by thunderstorms this morning, but the storms had not moved over to the Canterbury planes as originally feared.

"There definitely was some activity around Fairlie late this morning, and we've had some stuff in Lake Coleridge area as well, but generally most of the Canterbury planes has managed to escape so far, and there's probably very little chance now of anything turning up.

What is dry thunderstorm?

A thunderstorm and lightning that occurs without any significant rainfall.

How does it work?

Dry thunder forms when there is a lot of dry air beneath a thunder cloud, which is sitting high in the atmosphere. As the rain falls from the cloud, it evaporates in the dry air before it has the chance to hit the ground.

Is it common?

It is not very common in New Zealand, although it has been happening a bit in the past few weeks because of the hot and relatively dry air drifting over from Australia.

On average, New Zealand has about half a dozen dry thunderstorms a year, compared with a normal thunderstorm happening somewhere in New Zealand every two to three days.

It is more likely to happen on the east coast of both islands.