The company's North American site crashed after a power failure and other problems at a server farm, according to the Financial Post. The details of why have not been shared with the public.
The Vancouver-based firm relies on direct-to-consumer sales for about 17% of its revenue, estimates Macquarie analyst Laurent Vasilescu.
A website malfunction can take a significant toll on same-store sales, also known as "comps," Vasilescu told the Financial Post. A three-day outage would have cost Lululemon a penny in earnings per share, he added.
"Another way to think about it is that every day the website is down, the company's total company comp for that day is likely down double-digits," Vasilescu explained.
Shares of Lululemon were lower over 1.5% during afternoon trading on Tuesday.