A powerful thunderstorm wreaked havoc in Hawaii on Sunday and Monday, causing power outages and toppling trees and electrical lines across the islands.

Most of the Kona-low storm was expected to move away from the islands by today, but strong winds were expected to continue, National Weather Service forecasters said.

Hawaiian Electric responded to numerous outages that affected thousands of customers on Oahu, Maui and Hawaii island Sunday and Monday.

On Oahu, strong winds knocked out power to 8,580 customers in Kane­ohe late Sunday until early Monday when crews restored power.

More than 4,400 customers in Waianae and Nanakuli areas also experienced an outage Monday until Hawaiian Electric restored power to affected customers by 2 p.m.

An outage in West Oahu also affected 2,456 customers in Barbers Point, Kalaeloa, Kapolei, Ko Olina and 1,870 customers on the North Shore, including Haleiwa, Helemano, Kaena Point, Mokuleia and Waialua.

Hawaiian Electric crews also responded to outages in Kailua, Mililani and other parts of Oahu.

Honolulu Fire Department crews were busy responding to 18 calls of downed trees throughout the island from about 7:35 p.m. Sunday through about 7:45 p.m. Monday.

On Sunday night, fire crews extinguished a small fire in Kahaluu after electrical wires exploded and severed from a utility pole at about 8:15 p.m.

A caller pointed out a high-voltage wire touching a tree and arcing to responding fire crews in the 47-300 block of Lulani Street. The Fire Department said the electrical wires landed on the ground and on top of cars. “The arcing caused a small fire under a vehicle which was quickly extinguished.”

No injuries were reported.

The storm also caused outages in Hawi on Hawaii island and parts of Maui that include Upcountry, Haiku, Hana Olowalu, Lahaina, Wailuku, Spreckelsville and other areas.

Heavy rain and strong wind also prompted the closure of Puuhonua o Honaunau and Kaloko- Honokohau National Historical Parks on Hawaii island and the summit at Haleakala National Park on Maui.

Multiple roads on the Big Island were closed due to flooding and debris, officials said.

In addition, numerous Hawaii County facilities were shut down Monday due to lightning, fallen branches and tree limbs or other safety hazards. They include Konawaena Swimming Pool, Kona Community Aquatic Center, Honokaa Swimming Complex, Kawamoto Swim Stadium, Pahoa Pool, Kamehameha Park, Hisaoka Gym, Waimea District Park and the Hilo Municipal Golf Course.

On Maui, officials urged visitors to postpone planned trips to Hana Highway due to hazardous conditions after boulders, rocks and broken tree branches blocked a portion of the highway.

The hazardous conditions and limited access prompted the 5:30 p.m. opening of a shelter at Hana High &Elementary School, staffed by volunteers from the American Red Cross.

Remote Piilani Highway, between Kipahulu and Ulupalakua, was closed to traffic because of the storm, and flooding, road debris and unsafe weather conditions were blamed for the closure of the Central Maui Landfill.

The severe storm also led to the closure of popular trails such as Pipiwai Trail on Maui and Kalalau Trail on Kauai.

About 9,400 members of the Kauai Island Utility Cooperative experienced outages over the two-day period. “Outages were caused by high winds causing trees to interfere with power lines islandwide and lightning strikes to transmission lines on the west side,” said spokesperson Allison Young in a statement Monday.

Outages occurred in Kokee, Kekaha, Waimea, Hanapepe, Eleele, Kalaheo, Koloa, Lihue, Hanamaulu, Wailua, Homesteads, Kapaa, Kilauea, Princeville and Hanalei.

Forecasters said today should experience a slight decrease in wind, with showers over leeward areas. By Wednesday, they said, wind should be light, and fair weather is expected to return.

Beyond Wednesday, only light wind is in the forecast, but another front could approach the islands, and parts of Kauai and Oahu could see an increase of showers by the end of the week, they said.

Meanwhile, extreme-surf conditions were expected today for north- and west- facing shores of Oahu, Kauai, Molokai and Niihau, with forecasters predicting “dangerously large breaking waves of 30 to 40 feet” and powerful currents with waves breaking in channel entrances, making navigating the channels dangerous.