The weather Monday called for snow, but Overstock.com Inc. was experiencing its fourth day awash in customers.

Chief Executive Officer Patrick Byrne said the Salt Lake-based online closeout retailer had experienced wave after wave of shoppers looking for an alternative to in-store shopping from Friday through so-called "Cyber Monday."

"You've got to distinguish between the tide coming in and a tsunami hitting," he said Monday. "The tide coming in last year began around Nov. 5 and saw a big pickup. This year, the tide didn't really start coming in until around Nov. 15.

"On the other hand, the tsunami has hit. Really, the first breaker hit us Friday, and an even bigger breaker hit us today. The breakers are bigger than last year. The tide was a little bit lower and slower to arrive than last year, but when the tsunami has come, it's bigger than last year."

Byrne declined to provide many statistics but indicated that sales were up a double-digit percentage the past few days, compared to the same period last year. "We had a soft third quarter where we actually shrunk, so being up a double-digit percentage is nice," he said.

The wave that hit Friday, the so-called "Black Friday" for brick-and-mortar retailers, was 25 percent higher than Overstock.com had planned for, he said. "We've got 600 people at the warehouse, working 24/7, and we're caught up," he said.

And Monday's sales, he said, were three times higher than any sales during any Monday in October.

Cyber Monday, coined by the National Retail Federation's shop.org, has a reputation for being a big day for e-tailers like Overstock.com, but it usually is not the biggest. Overstock.com's largest sales day last year was Dec. 12, when sales were in the $7 million to $8 million range.

Byrne is expecting a repeat this year, likely between Dec. 10 and Dec. 14.

"Somewhere in there, there will be a day even bigger, more like 40 to 50 percent bigger (than Monday)," he said. "Cyber Monday, while it's the first really big wave, it's not the biggest. There will be four or five more big waves like this."

Internet research firm comScore Networks Inc. expects either Dec. 11 or Dec. 12 to be the biggest day for overall online sales, with Cyber Monday either the ninth- or 10th-busiest online shopping day. Last year, the first Monday after Thanksgiving was the ninth-busiest day.