The opening of Costco's $100 million Auckland store has been disrupted due to weather and ongoing construction delays.

The big box retailer had planned to open its three-story megastore at the end of the month, but it is now unable to commit to a date.

Costco managing director Patrick Noone said in a statement that construction of the Westgate building was continuing.

"Unfortunately, due to Covid-19 and weather delays, we are unable to provide an exact opening date at this time."

More than 700 people who had already signed up for a Costco New Zealand membership received an email informing them of the store delays.

By the time the store opened, about 350 people would have been hired, and Costco would bring in 30 to 40 staff trainers from Australia.