Hello summer: Storms before sun

The sun has arrived but may be accompanied by rain and possibly even isolated thunderstorms in the north and west on of the North Island. Photo / Paul Taylor

Thunderstorms are expected to hit some parts of the North Island today and tomorrow before temperatures soar to low-30s in some parts of New Zealand later this week.

The sun has arrived, but with it comes some rain and possibly even isolated thunderstorms in the north and west on of the North Island too.

Forecasters are predicting parts of New Zealand will reach low-30s by Wednesday and again on Saturday.

But in Northland and Waikato, Gisborne and Taupo the washing may not be safe on the line as WeatherWatch head weather analyst Philip Duncan warned there would be some afternoon heat showers and isolated thunderstorms today and tomorrow.

Auckland was unlikely to experience much wet weather as it was sandwiched between the two areas expected to bear the brunt of the storm, he said.

However, the hottest place to be was Napier and Duncan was confident it would reach low-30s on Wednesday.

"There is a high pressure system over the top of the country at the moment. It slowly drifts away to our east over the next day or two and, as the result of that, will bring in a very hot nor'wester that will see the rest of the North Island up to 30 degrees."

Thursday and Friday were expected to be slightly cooler, before temperatures soared again on Saturday - particularly on the eastern side of the country.

The South Island was expected to be slightly cooler with Christchurch reaching mid-20s on Tuesday and falling to 14C on Wednesday, while further south Dunedin is only likely to reach low-20s before dropping to mid-15s.

Duncan said the increase in high pressure systems coming to New Zealand was a good sign for Christmas day as it bodes well for drier calmer weather.

Despite the increase in temperatures, MetService meteorologist Claire Flynn said the figures were "sitting around average for this time of year", but most of New Zealand was warming up.