Hempfest organizers are making a do-or-die push to keep the 19-year-old event alive.

They say money is running out, and unless something changes, this could be Hempfest’s last year.

The event’s chief organizer, Vivian McPeak, said high operational costs outpaced revenue by leaps and bounds last year. Hempfest lost $50,000 in 2009, a deficit it has to make up at this weekend’s event in Myrtle Edwards Park.

“If we have another bad year, we’re probably not coming back,” McPeak said.

Hempfest has free admission but accepts donations to offset costs. McPeak estimates donations averaged out to about 15 or 20 cents for every attendee last year — not nearly enough to pay for insurance, signage, permits and other costs.

McPeak said it’s “a communication issue.” He doesn’t think fans of the annual cannabis event know what’s at stake if they don’t donate a few dollars.

This year, he’s hoping everyone will contribute $5 or $10. Volunteers will be more aggressive about soliciting donations from the crowd, and they’ll be able to run credit cards for the first time.

Hempfest has been a controversial Seattle fixture since it debuted at Volunteer Park in 1991. About 500 people attended that first gathering, billed as the Washington Hemp Expo.

The event has lately campaigned for the medical-marijuana movement.

Hempfest 2010 runs Saturday and Sunday at Myrtle Edwards Park, featuring hundreds of bands, speakers and vendors. The tents were already going up earlier this week — but if organizers had their way, they’d have gone up sooner.

Hempfest officials tried to obtain permits to start Hempfest on Friday this year, a move that would have made for a three-day festival.

“We feel that’s the natural evolution, for a three-day event,” McPeak said.

He estimates the extra day would have brought in $50,000 in revenue — exactly the deficit Hempfest needs to fill.

“Unfortunately we kind of hit a brick wall,” he said. The city rejected the application, citing budgetary reasons.

Now, a plea for 2011 is posted on www.hempfest.org: “We are asking supporters to call and write the mayor’s office suggesting that a third day is granted in 2011.”

If Hempfest ends its run this year, McPeak thinks Seattle tourism would take a hit. Hempfest is billed as the largest cannabis event in the nation, and many attendees come from out of town.

More than that, canceling wouldn’t look very good for the marijuana movement.

“If Hempfest goes away, that’ll be considered to be a good sign for our opposition in law enforcement,” McPeak said, quickly adding that the event has a good relationship with the Seattle Police Department.

The annual festival draws cannabis fans to Seattle every year, but event organizers say it’s more than an excuse spend a weekend celebrating marijuana.

Hempfest has an agenda, and it’s not all about changing laws.

Organizers say they want cannabis to become part of mainstream culture. This year’s event is themed “responsible use and harm reduction.”

If weather factors into attendance, Mother Nature could be packing a one-two punch for Hempfest. The National Weather Service is predicting a cloudy weekend, with temperatures in the 60s.

Hempfest isn’t the only Seattle event that’s facing down a budget shortfall — and publicly asking for help. Among other events in crisis, the city’s annual fireworks show was almost didn’t happen this year, and the Seafair Pirates nearly canceled their summer festivities when sponsors backed out.

In both of those cases, sponsors with deep pockets stepped up to help with financing.