Alpine Meadows and Mammoth Mountain received the artillery pieces on loan from the Army and began using them last year to fire rounds into mountainsides and knock snow loose.
But the ski resorts received word earlier this month that the Army's Tank Automotive and Armaments Command at the Rock Island Arsenal in Illinois needs the howitzers back immediately.
"I need to have them back in the troops' hands within 60 to 90 days," said Don Bowen, the Army command's team leader in charge of the howitzers. "It's a very short timeframe to get them serviceable and back into the theater in southwest Asia. Afghanistan-Iraq is the immediate concern."
The ski resorts said they will comply.
"Given it's a war effort, their needs are greater than ours," said Larry Heywood, Alpine Meadows director of mountain operations.
Howitzers are short-barreled cannons that can be pulled by a vehicle. They fire three to 10 rounds per minute at a range of 9,600 to 12,330 yards. Replacing one would cost around $1 million, Bowen said Tuesday.
The military lent two to Alpine Meadows and three to Mammoth Mountain.
Alpine Meadows and Mammoth Mountain are the only ski resorts in the nation using the 119-A howitzer, the most modern model available, said Bob Moore, a U.S. Forest Service specialist in Truckee, Calif. Other resorts have older 105 mm howitzers.
Pam Murphy, senior vice president at Mammoth Mountain just east of Yosemite National Park, said the military has provided the ski resort with recoilless rifles and other guns for avalanche control for 30 years. The howitzers are the most effective, Murphy said.
"It was designed to kill people, but it's a very valuable safety tool for us," said Rachael Woods, a spokeswoman at Lake Tahoe's Alpine Meadows, where seven people were killed in an avalanche in 1982.
Resort officials said they spent hundreds of thousands of dollars to transport the guns, reimburse the Army for training and build firing platforms.
But Murphy said she understood the Army's decision: "We're certainly at a different place in the world than when we first got the guns."
The Forest Service said it is working to secure older howitzers for the ski resorts, and the Army's Bowen said he is optimistic that will happen.