After passing Lillooet Lake, the highway climbs a steep grade to Joffre Lakes Provincial Park, and shortly after passes through Cayoosh Pass, the highest point on the highway at . East of the pass the road follows the course of Cayoosh Creek as it traverses the southern base of Mount Rohr and skirts Duffey Lake Provincial Park. As Duffey Lake Road, after winding almost northeast in very steep mountains where sometimes the speed limit is , Highway 99 reaches the junction with Highway 12 at Lillooet, and then goes northeast for another to its northern terminus at its junction with Highway 97, just north of Cache Creek and just south of Clinton. The speed limit of the Sea-to-Sky Highway ranges from with sections in Lions Bay, Britannia Beach and parts of Squamish.