Most investors would love for a stock to deliver a 20% return over the course of a year. But how about a return four times that level in just one month? Three marijuana stocks did just that in January.

Canopy Rivers (OTC:CNPOF), Cronos Group (NASDAQ:CRON), and Canopy Growth (NYSE:CGC) soared 80% or more in the first month of 2019. What lit a fire beneath these marijuana stocks -- and are they buys now?

Three marijuana leaves on top of a line chart going up.

Image source: Getty Images.

1. Canopy Rivers

Canopy Rivers is the cannabis investment platform spinoff of big marijuana producer Canopy Growth. Its share price tracks pretty closely with its parent's, but Canopy Rivers has been the bigger winner so far this year, with its shares skyrocketing 94% in January.

Both Canopy Rivers and Canopy Growth enjoyed a nice jump after Canopy Growth outlined its advantages in the fast-growing hemp-based cannabidiol (CBD) market on Jan. 9, 2019. But it was really off to the races for Canopy Rivers a couple of weeks later when the company announced its investment in Herbert, a brand platform that focuses on the cannabis beverage and edibles market.

Cannabis beverages and edibles aren't legal in Canada yet. However, regulations should be finalized later this year. Canopy Rivers thinks that its investment in Herbert could pay off nicely once the potentially large market for cannabis beverages and edibles opens for business.

2. Cronos Group

Cronos Group came close to being the top-performing marijuana stock in January, soaring 90% higher in the month. And Cronos accomplished this feat without announcing any major news. However, there were several potential catalysts for the stock.

One was the written response from U.S. Attorney General nominee William Barr reiterating his commitment to refrain from going after cannabis businesses. While Cronos doesn't have U.S. operations currently, Barr's written statement provided some reason for optimism that the Trump Administration would be more friendly toward the cannabis industry and perhaps even support changes to federal laws that would pave the way for Cronos to enter the U.S. marijuana market.

Another possible reason for Cronos Group's great month is investors' anticipation that the company's big partner, Altria, could soon buy up shares. The tobacco giant announced in December that it would buy a 45% stake in Cronos for around $1.8 billion. The transaction is expected to close in the first half of 2019.

3. Canopy Growth

Canopy Growth stock jumped 82% in January. You've already read about one reason behind the big marijuana producer's great month -- its public statement outlining its hemp CBD advantage. But there has been more to the story for Canopy Growth over the last several weeks.

The company was active on the international front in January. On Jan. 9, Canopy Growth announced the launch of Spectrum Cannabis Peru, its newest business in Latin America. The company already has a licensed production facility in Colombia and is conducting clinical trials of cannabinoids in Chile. And on Jan. 21, Canopy Growth announced the formation of a new business to provide medical cannabis products in the United Kingdom and its first import of medical cannabis for its subsidiary in Poland.

But the biggest news for Canopy Growth was its receipt of a license to produce hemp in New York and its commitment to invest in a hemp industrial park in the state. Canopy Growth announced on Jan. 14 that it plans to invest between $100 million and $150 million to build large-scale hemp production facilities, establishing the company's first major U.S. operations.

Check out the latest Cronos and Canopy Growth earnings call transcripts.

Are they buys now?

My view is that all three of these stocks could run into turbulence in the near future. A pullback is common after stocks rack up the kinds of gains that Canopy Rivers, Cronos Group, and Canopy Growth generated over the last few weeks. But does the possibility or even likelihood of volatility mean these stocks aren't good picks right now? Not necessarily.

It's absolutely true that the near-term revenue potential for the three companies doesn't justify their valuations. That's especially the case for Canopy Growth, which now sports a market cap of more than $16 billion. If you're a conservative investor or one focused on the short term, you might want to stay away from these high-flying marijuana stocks.

However, if you have an aggressive investing style and are looking at the long term, these three winners from January are worth considering. The global cannabis market will probably exceed $100 billion within the next 10 years or so. All three of these companies should be able to profit tremendously from this growth.

I personally prefer Canopy Growth and Cronos Group. Canopy Rivers is still relatively new, so I'd like to see the company develop more of a track record before taking a harder look at the stock.

Don't count on 80% returns every month for any of these stocks. But I think that Canopy Growth's relationship with alcoholic beverage maker Constellation Brands and Cronos Group's partnership with Altria put both companies in great positions to succeed as the global cannabis market takes off.