U.S. shores are unlikely to see a direct hit, but a strong offshore hurricane can produce massive and dangerous waves well away from its center.

After exploding in strength at a historic rate this weekend, Hurricane Erin is now a sprawling Category 4 storm churning in the Atlantic. The storm’s enormous footprint is becoming the biggest concern as it threatens to drive life-threatening rip currents and towering waves toward the eastern US coastline and Bermuda.