Police say that dismal summer weather means that the season has been a bust for B.C.'s biggest cash crop – marijuana.

Vancouver Island RCMP say they've noticed a big drop in the number of outdoor marijuana sites spotted from the air this year, and the crops on those sites contain fewer, smaller plants.

The likely culprits for the shrinking crops include lack of sun and cooler temperatures at the start of the season, according to a release.

Police destroyed just 7,281 plants from outdoor grows on Vancouver Island this year, just a fraction of the more than 30,000 plants seized in 2010.

An integrated team made up of officers from various RCMP detachments on Vancouver Island use helicopters to search for marijuana grows sites every year.

This year, the police say they discovered significantly fewer large-scale sites, which can include as many as 450 plants.

The airborne portion of the investigation is over but police said they will continue searching for illegal grow-ops from the ground.

While Mounties say cold summer weather played a role in this year's decline, they're also saving some credit for themselves.

"Our efforts over the past decade to destroy this annual crop appear to have paid off," Cpl. Darren Lagan said in a release. "The loss of over 30,000 plants last year alone sent a strong message to those responsible for this illegal activity."