(Portland, OR) -- Beachgoers need to watch for king tides this weekend along the coast. King tides happen when the sun and moon align to cause higher tides than normal. Large 15- to 18-foot waves are possible on beaches in Northwest Oregon and Southwest Washington. The larger waves can cause stronger rip currents and there can be more sneaker waves. You should stay high on the beach, don't crawl on logs, and never turn your back on the ocean.