Central Oregonians know: The 40th annual Sisters Outdoor Quilt Show will mean backed-up traffic.

Now the Oregon Department of Transportation is warning motorists to be prepared for “extreme congestion” during the show this Saturday.

According to ODOT, organizers expect even greater attendance than past years.

“Combined with highway traffic volumes already about 10 percent higher this year over last throughout Central Oregon, motorists traveling (U.S. Highway 20) through Sisters can anticipate extreme congestion along the detour route and on the eastern approach to Sisters.”

The traffic advisory is in place from 6 a.m. to 5 p.m. Saturday.