Any day now, WASH-FM, which appeals to a mostly female suburban audience with the music of Josh Groban, James Taylor, Elton John and Celine Dion, will switch over to the Christmas sounds of Andy Williams, Burl Ives and Jose Feliciano.

Like hundreds of adult contemporary stations that go all-Christmas from about Thanksgiving till the end of the year, WASH (97.1 FM) scraps its regular format both because the holiday tunes bring an immediate boost in ratings and because the listeners brought in by the Christmas marathon tend to stick around when the station reverts to its usual fare.

"Every year it brings a new audience to the station," said Jeff Wyatt, regional vice president for programming at Clear Channel, which owns WASH. "People who are Christmas-inclined seek it out, and others just find it and like it, and then they stick around the rest of the year."

Folks who have only a limited tolerance for "Holly Jolly Christmas" and "Jingle Bell Rock" may tune away, but their numbers are not enough to dissuade WASH and other all-Christmas stations from their chosen path. "I don't know if Jewish people turn it off; we haven't measured that," Wyatt said.

Other stations add a lot of holiday music to their play lists as the big day approaches, and WGMS in recent years has gone all-Christmas in a classical vein in December. But the total Christmas experience is a relatively new phenomenon in radio, dating back to the mid-'90s, and the start date, like the launch of the holiday shopping season, creeps ever earlier on the calendar.

"We start it up sometime in the first days after Thanksgiving," Wyatt said, "depending on the weather and just how Christmasy it feels." But in markets where more than one station goes all-Christmas, the start date can push all the way up to Halloween as stations jockey to be the first to make the switch.

A study by Sean Ross, vice president of music at Edison Media Research, found that 71 of 119 stations that went all- Christmas got an immediate ratings boost. Two-thirds of those stations saw their numbers droop a bit after they returned to their regular formats, which raises a question: All-Christmas, all-year?

For that, you have to head to the Internet, to ChristmasRadio.com and a bunch of other Web stations where the Eagles beg eternally, "Please Come Home for Christmas."