It is not yet believed that the shortage will impact on the availability of fresh potato stocks.
Wet conditions right through winter have had two effects on crops, Pukekohe Vegetable Growers Association president Brent Wilcox said.
"Planting up new season crops, growers haven't been able to plant the crops on time because the ground's been so wet," he said.
Other crops have been lost because the potatoes have been in the ground over winter, and the wet conditions have caused them to rot.
Wilcox said the financial impact was "millions of dollars" for farmers, who may struggle for the rest of the year to return supply to normal.
"It's been quite stressful for growers . . . some growers have lost crops, they've been flooded."
Wilcox said wet weather impacting potato growing happened "to an extent" every year, "but this is quite, perhaps, more extreme than it has been for a while."
Shoppers would have noticed prices for potatoes and potato products had "firmed" in the last month or so, he said.
New Zealand was last hit by a potato shortage in late 2014 to early 2015 for similar reasons.
Meanwhile the same problem hit Japan earlier this year, according to CNBC.
Bad weather in the northern island of Hokkaido, where 80 per cent of the country's potatoes are grown, meant spring potatoes only reached supermarkets in late May.