The first snowfall, massive sales and retail store aisle assaults. Yes, the holiday shopping season is upon us.

Black Friday weekend featured a substantial uptick in shopping compared to 2009. $45 billion was spent at American stores last weekend compared to $41.2 billion in 2009, according to a survey conducted for the National Retail Federation.

Matthew Shay, the president and CEO of NRF, said in a press release that it is important for retailers to keep the good-sales momentum going in the coming weeks.

“While Black Friday weekend is not always an indicator of holiday season performance, retailers should be encouraged that a focus on value and discretionary gifts has shoppers in the spirit to spend,” Shay said.

Matteo Arena, a professor of finance, said the success of the end of the year sales in the retail business can make or break certain companies.

“A few firms incur net losses the first three quarters of the year and make all their profits in the fourth quarter,” Avena said in an e-mail. “Toys R Us is a typical example of this.”

Richard Robinson, a professor of marketing, also emphasized the importance of November and December sales.

“A few key sectors must do well in the holidays,” Robinson said. “Retail, particularly toys and other seasonal businesses like florists and jewelers, restaurants, travel, and nonprofits, which many overlook, (host) big holiday events.”

According to the NRF survey, Black Friday featured an increase in the number of shoppers, average amount of money spent per shopper, and shopping on Thanksgiving Day.

Both Arena and Robinson said the Black Friday sales indicate the U.S. economy is slowly rebounding from its recessionary state.

“Given that retail and restaurants account for one in five jobs in the U.S., Black Friday must deliver the numbers for retailers in particular,” Robinson said. “Since it was up over last year, it could help lead us further into recovery.”

Robinson pointed out that holiday sales extend far past Thanksgiving weekend.

“More consumers (are) procrastinating and therefore, causing retailers to closely monitor those last few days of the holiday buying season,” he said.

Cyber Monday, the first day Americans go back to work after Thanksgiving, is one of the bigger Internet shopping days of the year. It also saw an increase in sales and deals offered by online retail companies, a separate NRF survey said. Arena said the increase in Internet sales could be due to the fact websites are becoming more adept at attracting customers.

Phil Rist, the executive vice president of BIGresearch, which conducted the Black Friday survey for NRF, said Internet shopping is only going to become more prevalent in the future.

“Many businesses understand that Americans’ work and personal lives are merging, and would rather have employees shopping online at work than driving all over town during their lunch hour looking for the perfect gift,” Rist said in a press release.