FedEx shipped more than 19 million packages Monday — making it the single busiest shipping day in company history. According to company numbers, 300,000 FedEx workers nationwide, along with approximately 20,000 seasonal personnel, processed more than 200 packages per second.

According to Susan Rosenberg, spokeswoman for UPS, the Atlanta-based shipper’s peak day will be Dec. 20, when more than 28 million packages will be delivered. She says a normal average daily volume is 15.8 million.

UPS expects to deliver 135 million packages next week of the 527 million it has forecasted for the period between Thanksgiving and Christmas.

“One important note is this year’s impact of increasing online shopping,” Rosenberg said. “We’ve seen the trends building to compress the holiday shipping just before Thanksgiving through Black Friday and CyberMonday week, and then again in the two weeks before Christmas as there is more technology penetration and mobile devices for online shopping.”

Jim Strouts, operations manager for two UPS franchise retail locations in East Cobb and Kennesaw, left FedEx for UPS earlier this year. He said that for the retail side, the blitz begins much earlier. Stouts said that at his store, located on Johnson Ferry and Woodlawn roads in East Cobb, customers began flooding in the first day of the month.

“We saw a 50 percent increase in business starting on Dec. 1, and it has steadily risen to 150 percent above normal average packages per day,” he said.

Kelly Todd, senior manager at FedEx Ground’s regional hub in Kennesaw, said an additional 100 seasonal hourly workers were hired at his facility for package processing. The facility, which is part shipping hub and part customer center, operates 24 hours a day, and work days have been extended to six days a week for the season.

Todd says FedEx prepares for December for 11 months of the year.

“We have detailed forecasts and predictions that are updated weekly all year long,” he said. “We anticipate this month all year based on our customers and their forecasts.”

Todd says FedEx has year-round shipping contracts with companies and cataloguers as well as seasonal shippers that are factored in to these forecasts. The company is reporting a 10 percent year-over-year increase in volume from 2011.

Online holiday sales are forecasted to climb 17 percent compared to last year, according to digital marketing and commerce publisher eMarketer. Online auctioneer eBay coined Dec. 10 as “Green Monday,” to describe the traditional kick-off to the heaviest online shopping week of the year. According to comScore, in 2011 U.S. consumers spent $1.1 billion on Green Monday.