April 20 may one day be akin to the Black Friday of the marijuana industry — that is, if weed shops in America ever have any trouble moving their product during the rest of the year.

Sales of pot on the day — which is celebrated as something of a holiday by enthusiasts of the substance — increased dramatically this year in Colorado and Washington, both of which legalized recreational weed about four years ago, according to MarketWatch. In Colorado, retail sales spiked by more than 50 percent compared with the year before. In Washington, sales nearly doubled this year.

That surge in purchases broke sale records in Colorado, which were last set in September on a tax holiday. Weed sales reached $7.3 million April 20 of this year, up from $6.1 million Sept. 16. Those sales also led to a record-breaking month, with $117 million in sales beating out December, when $101 million worth of marijuana was sold.

marijuana2 Dave Warden, a bud tender at Private Organic Therapy, a nonprofit co-operative medical marijuana dispensary in Los Angeles, displays various types of marijuana available to patients, Oct. 19, 2009. Photo: David McNew/Getty Images

Colorado and Washington are two of five states in the United States that have legalized recreational marijuana. They are joined by Alaska and Oregon, as well as the District of Columbia. As many as eight states could soon be added to that list: Massachusetts, Nevada, California, New York, Vermont, Minnesota, Connecticut and Maryland.

Many more states have legalized medical marijuana, which can be used to treat chronic pain, epilepsy and the side effects of cancer treatments. Less than a week ago, Ohio became the 24th state in the union to approve medical pot when former Republican presidential candidate and governor of the state John Kasich signed legislation to that effect into law.

The ballooning number of states with legal marijuana on the books in some form or another have created a huge industry. This year, it was estimated that pot sales in total account for a $5.4 billion industry in the U.S.