Denver - Pot may be legal in Colorado, with people lighting up at rallies in Colorado for more than 20 years, but Denver Police are reminding people it's technically illegal to smoke it in public.

Organizers hope this year's rally at Civic Center Park will be as big as any other year, despite rain in the forecast.

Gates open at 10 a.m., and there's a free concert at 2 p.m.

Rapper 2Chainz headlines at (surprise?) 4:20 p.m.

Vendors and pot businesses are lined up for events around town all weekend but Denver Police are warning people it's not exactly a free-for-all.

RELATED: Marijuana's big day is here: '420' celebrations ready to roll

They arrested 79 people around this event last year, 64 for pot-related charges.

To help you stay out of trouble, they want to remind people of a couple of points:

  • You have to be 21 to buy or smoke pot in Colorado.
  • You cannot sell or give pot to anyone under 21.
  • It's still illegal to smoke in public, and DPD officers can still ticket you at their discretion (though the department typically takes more of an observational and public safety role around 420 events.)
  • You can only sell pot if you have a license to do so.
  • It’s illegal to drive high.

The rally organizers have partnered with Uber to help you out with the last one. 

If you use the code SAFE420 in Uber today, you can get $4.20 off your Uber ride.

Keep an eye out for mini mile marker 420 signs at events all weekend.

They're an homage to the Interstate 70 mile markers that kept getting stolen in Eastern Colorado.

The Colorado Department of Transportation produced these mini-signs with Lyft.

If you find one, it's worth $42 for Lyft rides this weekend.