Hurricane Nolo's 20-Inch Rain Threat Exposes Hawaii's Climate Vulnerability

For climate and energy professionals, Hurricane Nolo is a live case study in compound climate risk: a slow-moving storm dropping up to 20 inches of rain on terrain already saturated by August's Hurricane Lala. The potential for tree and power line damage, flash flooding and mudslides raises urgent questions about grid hardening, emergency power resilience and adaptation funding. As Nolo churns south of the Big Island with 90 mph winds, Hawaii's experience offers early signals for how island grids and communities will cope with intensifying tropical cyclones.

On the morning of Sept. 27, 2026, Hurricane Nolo was churning slowly south of Hawaii's Big Island with maximum sustained winds of 90 mph, its center about 165 miles south-southwest of the island's southernmost point. The National Hurricane Center had canceled a hurricane watch and no direct landfall was expected. Yet the storm's outer bands were already inflicting significant damage: heavy rain caused partial closures of Mamalahoa Highway near Naalehu, and rainfall totals on parts of the Big Island were projected to reach 20 inches. Forecasters warned of life-threatening flash flooding and mudslides, while Nolo was expected to strengthen into a major hurricane late on Sept. 27 and into early Sept. 28 as it moved westward south of the islands.

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Yet the storm's outer bands were already inflicting significant damage: heavy rain caused partial closures of Mamalahoa Highway near Naalehu, and rainfall totals on parts of the Big Island were projected to reach 20 inches.

The emergency response underscores how even a near-miss can strain island infrastructure. Hawaii's governor issued an emergency proclamation, and roughly 400 Hawaii Army National Guard members were activated statewide, more than 120 of them on the Big Island. On Sept. 26, guard members were seen helping a resident navigate flooded streets in Naalehu as he attempted to leave his home. Michael Brennan, director of the National Hurricane Center, urged residents not to venture out, citing dangerous flooding, high winds, downed trees and power lines. Humanitarian group CORE and its partners spent the week air-cargoing camp stoves, hygiene products and other supplies from Oahu to a Big Island community relief hub that has been operating since August's Hurricane Lala. Residents were still recovering from Lala, which brought heavy rain and strong winds, leaving communities more vulnerable to Nolo's compounding effects.

Nolo's slow forward motion and intensification are consistent with patterns climate scientists have observed in a warming ocean. The storm's projected rainfall of up to 20 inches is substantial for Hawaii's steep volcanic terrain, where saturated soils quickly trigger flash floods and mudslides. The hurricane season in the Central Pacific already saw Hurricane Lala in August; now, weeks later, Nolo is testing recovery efforts. Warm sea surface temperatures provide more energy, while slower storm movement can increase rainfall duration. Although Nolo's center stayed offshore, its vast outer bands delivered heavy rain across the island chain, an illustration of how tropical cyclone impacts extend far beyond the cone of landfall.