Fonterra is shipping some North Island milk across Cook Strait for processing in Canterbury, as northern dairy farms hit their peak production.
Fonterra operations and logistics director Robert Spurway says the co-operative sends milk in both directions from time to time.
He says the North Island always hits it peak milk flow earlier than the south, and the surge in production from the excellent spring means processing plants in the north are already running at full capacity.
Mr Spurway says for the season to September, milk flow was up about 5% on the same period last year. So far in October it is up about 3.5% on a year earlier.
"Whole milk powder is at seasonally high prices, so by shipping milk to the South Island we're able to make more of that milk into whole milk powder," he says.
"All our North Island plants are full. The flush of the season is this week and the flush in the South Island is another two or three weeks away, so it gives us the opportunity to use available capacity."
Mr Spurway says Fonterra expects to keep shipping some North Island milk to the south for another two to three weeks.
Most is being processed at the new Darfield plant in Canterbury.