Weather: South Island to bear brunt of summer inferno

Temperatures are continuing to spike on Tuesday as the heatwave continues to roll over New Zealand.

The South Island is set to scorch with forecasts of 37degC for Alexandra. Dunedin and Queenstown will both hit 31degC, while Oamaru will swelter on 29degC and Invercargill will hit 30degC.

The heat has already claimed one woman's life in Christchurch. The woman, who was in her early 60s, died last week from hyperthermia after overheating in high temperatures.

"There has been official heatwave conditions in parts of Central Otago over the last 5 days as stations such as Queenstown, Wanaka and Alexandra have all had temperatures about 30degC and higher," MetService warns.

"Most parts of the country have been well above their average and January is looking on course to be New Zealand's hottest on record."

There are warnings the temperatures today could be the hottest so far - although not as bad as previous records.

On the West Coast, Milford Sound, Hokitika, Greymouth and Westport are forecast to reach 25degC.

The Canterbury and Marlborough region will be hammered by the heat, with everywhere from Timaru to Blenheim reaching over 30degC.

The lower North Island faces another hot summer's day, ranging from 26degC for Wellington to a scorching 34degC for Masterton.

The middle of the North Island will linger under 30degC, with highs of 29degC in Whanganui and Hastings.

The top will be a little bit cooler, ranging from 28degC in Hamilton to 26degC in Kaitaia.