Summer's back for the North Island

The thunderstorms and heavy rain that lashed the North Island on Tuesday are over, leaving New Zealand with hot and humid conditions.

Temperatures around the country are expected to spike over 30degC, leading to sweltering days.

Kiwis are pouring to the beaches to escape the heat - although the warm sea temperatures mean it's harder to cool off.

However there's no escape from the sleepless nights.

On Monday night humidity levels reached the highest point measured this summer, well into the uncomfortable range.

Temperature overnight have remained above an 18.6degC average since January 1. Wellington has had average overnight temperatures of 16.1degC.

It's the perfect breeding conditions for mosquitos, which thrive in the warm and wet.

Worse, the sticky weather is expected to last well into February.