Interstate 5 passes through the Siskiyou Mountains at Siskiyou Summit, located just north of the Oregon-California border, and just south of Ashland, Oregon. Siskiyou Summit is the highest pass on Interstate 5, at . This pass is one of the most treacherous in the Interstate highway system. The California side has a more gradual slope than the Oregon side, where the freeway climbs or descends in elevation over about . In addition, the pass includes several hazardous curves, and is frequently hit with snow, ice, and fog during winter storms. In winter, it is common for the highway to be closed one to four times per year by transportation authorities due to hazardous conditions. The speed limit is , but lower limits are set for larger vehicles.