Weather: Grim weekend delivers downpours, thunderstorms, lightning strikes

New Zealand is bearing the brunt of "unstable" weather this weekend with lightning, heavy rain and strong winds.

"Our lightning detection network has picked up around 2000 lightning strikes on an active front near Fiordland and western Southland in the past two hours. Heavy rain has been recorded too," MetService tweeted on Saturday morning.

The bulk of the rain on Saturday will be in the west and north of the South Island where orange warnings are in force, although the North Island will some rain too.

One rain station in Westland has already recorded more than half a metre of rain during the past few days.

However the bad weather will really ramp up tomorrow, with NIWA warning the worst of the weather will occur on Sunday and Sunday night.

"Sunday looks to be an atmospherically unstable day around Aotearoa with areas of downpours and thunderstorms," it says.

MetService says the rain will spread to all areas on Sunday as an active front moves slowly eastwards over the country from the Tasman Sea.

"Further heavy rain is forecast for the already saturated west of the South Island ahead of the front, and the risk of heavy rain spreads northwards to northern and western parts of the North Island. In addition, there is a risk of thunderstorms for many regions," it says on Facebook.

"The front is also preceded by strong to gale force winds in exposed places, and strong wind watches have been issued for several areas."

Newshub.