The prohibition of recreational cannabis ends Wednesday Oct. 17.

For a lot of investors, this might be the alarm bell to start investing in cannabis, but Cramer says that investors have missed their chances if they're not already in companies such as Tilray (TLRY , Canopy Growth (CGC - Get Report) , or Green Organic Dutchman (TGOWF .

The reason behind Cramer's advice is due to the fact that both Canopy and Tilray skyrocketed yesterday. Both stocks were up double-digits by the time that trading closed for the day.

In his Morning Jolt newsletter, Jacob Sonenshine wrote about cannabis. 

"Don't be so quick to assume that newly relaxed regulations on cannabis in Canada means a huge market expansion for the entire industry. The new regulations will become official on Wednesday, Oct. 17, making adult use of cannabis legal in all parts of Canada, with specific regions maintaining authority to adjust the rule in some ways," reported Sonenshine "Pot stocks surged on the news. Tilray Inc. ( TLRY) popped 11.69% on Monday, Canopy Growth Corp. ( CGC) rose 14.24%, Medmen Enterprises Inc. ( MMNFF) rose 9.59% and Aurora Cannabis Inc ( ACBFF) rose 11.03%."

Cramer's teach in, which was held in Manhattan on Saturday, Oct. 13, focused heavily on cannabis. Cramer interviewed Bill Newlands, Constellation Brands (STZ - Get Report) COO, and Canopy Growth's CEO Bruce Linton.