Sunny, clear skies and temperatures heading towards 30C are in store for much of the day as a ridge of high pressure continues to linger over the country.

The first weekend of the summer has been a scorcher and, bar the chance of thunderstorms in some places, sunny weather should continue for the rest of the day.

By 11am temperatures in some parts of the country were already pushing 29C in both islands and were expected to climb, Weather Watch head analyst Philip Duncan said.

The hottest weather would be inland where for some the daytime high would rest about 8C above average for this time of year.

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"Despite a brief cool down for some mid this week, the heat returns by the end of next week," Duncan said.

"Coastal areas won't be as hot for the most part, but should still be warmer than average."

Departures from average temperatures - the darkest red show areas more than 8C above normal today. Photo / The Weather Company
Departures from average temperatures - the darkest red show areas more than 8C above normal today. Photo / The Weather Company

In the South Island Clyde, Alexandra and parts of the Canterbury High Country were expected to hit 30 degrees today and further north Hastings, Featherston and Martinborough were all heading for 27 degrees with clear skies.

Yesterday temperatures hit levels usually not seen till much later in the season.

Temperatures near Christchurch topped 30 degrees yesterday - much higher than the summer average of 21C.

It will be another hot one for the southern city today, with a high of 28C predicted.

MetService meteorologist Ciaran Doolin said a persistent ridge of high pressure was the reason for the warm weather - and for sudden thunderstorms which could follow, particularly in the afternoons when the day was at its hottest.

Hot and sunny weather is forecast for Christchurch again today. Photo / Mark Mitchell
Hot and sunny weather is forecast for Christchurch again today. Photo / Mark Mitchell

High pressure meant settled conditions and typically clear skies, which was conducive to good exposure to sun, meaning warmer temperatures, he said.

"On the other hand, because things warm up so much it can also lead to the development of convection, which in its mature form leads to thunderstorms."

Thunderstorm risk areas were the Gisborne ranges and the western parts of Northland.

Isolated heavy showers were expected in the Marlborough ranges.

"Otherwise it should be a mostly fine day across most of the country."

Wellington was fine this morning with wind expected to pick up later in the day, a high of 22C, and Auckland could expect a fine day apart from isolated afternoon showers and a high of 24C.

Hamilton could be in for some thundery showers this afternoon with a high of 25C, and Napier could expect a high of 26C and a fine day with light winds.

Nelson had a forecast high of 25C with light winds and in Queenstown the high is forecast to be 26C with some cloud.