Weather: Why the South Island's heatwave is bad news for some

While North Islanders are still drying out, parts of the south are experiencing extreme heat.

Canterbury is already undergoing a dry summer and is set to reach 30C and higher three days in a row. While it's a glorious summer for some, it's bad news for many others.

It may seem a dream for North Islanders who've had a long wet summer, but the city soaked in the sunshine has issues of its own.

"Christchurch is forecast to see three consecutive days of over 30C temperatures. This is relatively rare in the 70 years of records," said Lewis Ferris from Metservice.

Simon Wallace from the Aged Care Association said this can be really challenging for older people.

"It can aggravate conditions for vulnerable and elderly people," he said.

And Wayne Hamilton from Fire and Emergency said it is a "recipe for disaster, really".

This is the case for firefighters because a wet start to the season means more growth than usual, growth that's now dried off and becoming fuel for fires. 

And now there are a few solid days ahead of blistering heat.

"Now we have a lot of vegetation around, coupled with the extremes of high temperatures, high wind and low relative humidity," Hamilton said.

It can also prove deadly for the elderly and frail.

"It can aggravate their conditions, for example, cardiovascular or respiratory disease," Wallace said.

MetService is now trialling issuing heat alerts in extreme bouts of hot weather.

"These next few days, parts of the south will likely have these heat alerts issued just purely because of how unusual the heat is and how prolonged it is as well," Ferris said.

Fire and Emergency is warning that this hazard is less obvious than flooding but still has the potential to be just as deadly.

"Effectively in the same situation as Auckland where there were floods, but here there's another bad forecast coming but it is obviously completely opposite. Here it's hot, dry and windy and relatively low humidity," Hamilton said.

So while South Islanders may have ample time to walk off into the sunset, walking inside and into the air conditioning might be a better bet for now.