Prime Minister Jacinda Ardern has met California Governor Gavin Newsom in San Francisco and signed off on a climate change agreement which will involve sharing technology and projects in areas such as electric vehicles and agriculture.

Ardern and Newsom - a Democrat many believe could be a contender for president - clearly hit it off.

Newsom began by praising Ardern's leadership after the Christchurch mosque attacks, and later said he was humbled and honoured that Ardern, as the leader of a country, had wanted to meet him as a state governor.

"You're quite a large economy," Ardern replied to laughter.

Ardern said NZ had put $2.9 billion into its Emissions Reduction Plan, and assured Newsom that was no small matter. Newsom had just said California's budget was $US47.1b (NZ$72b) .

She said she had invited Newsom to visit New Zealand and told him she hoped the agreement would help New Zealand met its Emissions Reductions Plan targets, especially in transport.

The Cash for Clunkers scheme announced as part of the Budget package for that plan was based on one already in place in California.

However, meeting that would depend on electric cars: "We need to source them."

Newsom said climate change was an "existential crisis" in California, which was experiencing bush fires and droughts it had not experienced a decade ago.

"The hot is getting much hotter, the dry is getting much drier, the wet is getting much wetter."

The event was held in the New Zealand garden area of the San Francisco Botanical Gardens - but the proximity of the Australian garden had led to the last-minute covering up of a sign that said Australia.

Ardern apologised to Newsom for the quality of the waiata singing by the business delegation: "It might not have been our best work but it came from the heart."

Newsom clearly was not too bothered by it - when the delegation sang again after Ardern spoke he jokingly asked why nobody had sung after he finished speaking.

Ardern heads to Seattle this afternoon for a meeting with Amazon.

The California agreement will include zero emissions vehicles, energy storage and smart grids, emissions trading schemes and agriculture.

Ardern said transport and agriculture emissions were issues for both NZ and California, which had similar emissions reduction plans.

"Gains here can be both good for business and the planet.

"We both aim to achieve net zero carbon emissions by the middle of the century. This agreement means we'll work together to share expertise and experience and collaborate on projects that help meet each other's targets."

The agreement is being pitched as opening opportunities for NZ businesses that can offer climate-friendly goods and services.

It coincided with the announcement of a deal between the NZ Merino Company's ZQRX and Silicon Valley tech platform Actual.

ZQRX is partnered with companies such as Allbirds and Icebreaker.

Ardern said the deal to help reduce the environmental impact of the industry was an example of the partnership she hoped the new deal with California would include.