More here(including video):

http://www.stuff.co.nz/national/7612344/Roof-lifted-off-house-in-Christchurch-storm

A roof lifted off a house and conservatories collapsed as a storm that hammered Christchurch this evening.

Brilliant displays of lightning and roaring thunder were followed by hail storms that caused damage in some parts of the city. The dramatic thunderstorm started just after 6pm and lasted about an hour.

A Fire Service spokesman said crews attended more than 20 storm-related incidents between 6.30pm and 7.30pm.

‘‘We had callouts relating to alarms being activated by water getting into the system and then we helped people make their houses weathertight too,’’ he said.

Conservatories collapsed in Hornby and Redwood, he said.

‘‘We investigated a couple of lightning strikes on properties but there’s been no reports of fire.’’

The storm has also caused a power cut in Southbridge, a small town south of Christchurch. Orion hoped to have power restored by 9.30pm.

Riccarton resident Louis Russell said the thunder was "pretty crazy" and was "lighting up the whole sky".

Ramzey Rosy said some of the hail was bigger than the size of a pea and it quite scary to go out in.

MetService said many parts of the country received thunder and lightning storms today but some Christchurch residents said hailstones had been the ''size of ping pong balls''.

Photos of hailstones up to 4cm wide have been sent in by Stuff readers.

If hailstones were larger than 2cm the storm was classed as severe, he said.

''Thunderstorms were on the radar for the Canterbury plains but we weren't sure whether it would hit the city or not but obviously it had and that would be a first in about two or three years, maybe even longer.''

At about 7pm there had been almost 300 lightning flashes in Canterbury, Gorman said.

''It's the sort of storm we would typically see in the summer but it's been a while since the city of Christchurch had one,'' he said.

The storm had developed over the Canterbury Plains near Ashburton this afternoon and moved northeast blown by a southwest wind.

Thunderstorms had also occured in Buller, Northland, south of Wellington and the Waikato today.

-  A previous version of this story reported that the storm had developed over Weka Pass about 2pm.

Stuff.co.nz

Just noticed this afternoon that the bonnet of my Ford Courier ute has many small round dents from yesterdays hail. You only notice them in certain light conditions. Interesting that it's only the bonnet and not the roof.
Bummer!!