Weather: Wet weekend ahead as MetService issues heavy rain watches across New Zealand

It's looking like a wet weekend ahead for most of the country as heavy rain watches have been put in place throughout New Zealand, affecting the central North Island and the far south.

The rain watches have been put in place by MetService as a low over the Tasman Sea is likely to spread unsettled conditions across the country.

"Taupō, Taumarunui and inland areas of Waikato and Waitomo from 3pm today until 3pm Sunday. Southland, Stewart Island and Clutha from 1pm until 10pm today," a post on MetService's Twitter page said on Saturday.

There is also a possible chance of thunderstorms throughout Aotearoa from Saturday afternoon right through to Sunday afternoon.

"An unstable atmosphere today means there is plenty of potential for thunderstorms.

"Keep an eye on the forecasts and the rain radar before heading out," MetService said.

The lower South Island including Dunedin and central and north Otago highly at risk of thunderstorms throughout Saturday.

MetService said on its website the thunderstorms could result in hail of up to 15mm and rain of up to 25mm per hour or possibly more.

The only major city appearing to dodge the wet weather is Christchurch, which is expected to reach a high of 25C.