Ala Kahakai National Historic Trail

Flash flooding is the clearest environmental threat along Ala Kahakai National Historic Trail, with Hawaii County recording 9 combined flood and flash flood events in recent years. The trail hugs the Big Island's lava coastline, where low-lying sections can flood rapidly when heavy rain strikes the inland slopes above, even under clear coastal skies. These events can cut off trail segments with little warning.

Before heading out, check the National Weather Service Honolulu forecast specifically for windward Big Island rainfall, since storms inland directly drive coastal flooding here. Carry a waterproof phone case and have offline maps downloaded so you can navigate to higher ground if water starts moving across the trail. Wear grippy, closed-toe water shoes rather than sandals — lava rock becomes dangerously slick when flooded, and a quick retreat over wet terrain demands solid footwear.