PTC One-C Heads Toward Hawaii; Life-Threatening Floods Possible

A tropical system east of Hawaii, currently designated Potential Tropical Cyclone One-C, is expected to strengthen and likely earn the name Hernan by Friday. Forecasters expect heavy rain to reach the Big Island Friday, spreading to Maui and the rest of the islands over the weekend. Rainfall totals of 5 to 10 inches are expected across much of the island chain, with up to 20 inches possible in some spots, raising the risk of life-threatening flooding and mudslides, especially in mountainous areas. Gusty winds could also down trees and power lines. Forecasters cannot yet say which spots will get the heaviest rain, so anyone in Hawaii should keep an eye on the storm's path over the next few days.

For homeowners on the islands, this is a reminder to check that gutters, drains, and yard grading can handle heavy runoff, and to make sure emergency supplies and backup power plans are ready in case winds or flooding knock out electricity. Only two tropical storms have made direct hurricane-strength landfall on the Big Island in recorded history, and the most recent close call was Hurricane Hone in 2024, so a direct hit is uncommon but not unheard of.

Elsewhere, the Eastern Pacific hurricane season is running ahead of its usual pace, with seven named storms so far. In the Atlantic, Tropical Storm Cristobal formed but is expected to fade quickly over cooler water, and two tropical waves are being watched but pose no current threat to the U.S. mainland.