However, growers say there will be plenty in stock in time for Christmas.
Warrick Macdonald of Blueberry Country, New Zealand's largest commercial grower, said the slight delay should not affect the price or availability of fruit once the harvest began in earnest.
"We'll have that volume of fruit coming through until the end of February and March and it really shouldn't make a difference," he said.
Although the weather had delayed fruit ripening by at least a fortnight, he was confident it would not affect volumes.
This week's warm weather should quickly ripen the fruit, with picking about to start. "Our expectations are that over the next few weeks the volumes would really start to ramp up," he said.
Outdoor picking began at Cambridge-based Monavale Blueberries yesterday, general manager Marco de Groot said.
This was 12 days later than last year, he said.
He described the spring as "tricky".
"My parents have been growing blueberries since 1985 and they are saying it's the coldest, windiest spring they can remember."
Recent low early morning temperatures had caused concern and the hail forecast for last month also produced scary moments.
But the challenging weather had not affected the crop's volume, he said.
"It's shaping up to be a pretty good season, be it later than last year."
The blueberry market was worth $28 million in 2012 - $10m in domestic sales and $18m in exports.
The industry employs about 2000 people and about 1800 tonnes of blueberries were grown in 2012.