Hurricane Lala approached Hawaii with strong winds and heavy rain on Saturday, leaving more than 40,000 utility customers without power across the state as the National Hurricane Center warned of “life-threatening” conditions.

The poweroutage.com website showed 42,889 customers without power as of 2:14 p.m. HST in Hawaii, including 31,792 on the Big Island and 7,203 in Maui County, which includes the islands of Maui, Lanai and Molokai.

An advisory from the hurricane center at 2 p.m. HST predicted 10 to 20 inches (25.4 to 51 cm) of rain on the Big Island, and possibly up to 25 inches there, as well as 8 to 12 inches in eastern Maui and 4 to 6 inches in western Maui.

“This rainfall will produce life-threatening flooding and mudslides, especially in areas of steep terrain,” the center said.

Hawaiian Electric warned customers to expect “possible extended outages, potentially overnight,” as the storm system made its way westward across Hawaii. On the Hamakua Coast on the Big Island, utility crews were assessing a 42-mile (67.6 km) span of transmission lines after fallen trees knocked down multiple poles and structures, Hawaiian Electric spokesperson Darren Pai told TV station Hawaii News Now.

Earlier in the day, the U.S. National Hurricane Center said Lala’s maximum sustained winds reached 75 mph (120 km/h), making it a Category 1 hurricane.

The Maunakea Weather Center, on the Big Island’s tallest peak, recorded wind gusts of more than 100 mph throughout the early afternoon, although winds would have been slower closer to sea level.

The Hawaii Department of Transportation said it was closing Hilo International Airport and would close Ellison Onizuka Kona International Airport at Keahole at 2 p.m. HST. The department also closed the Hawaii Island, Maui County, and Kaua‘i commercial ports.