Nearly two feet of rain fell on parts of Hawaii’s Big Island as Hurricane Lane approached the state early Friday, causing heavy flooding and landslides that blocked roads — with the worst still yet to come, according to forecasters.

Lane weakened to a Category 2 storm on Friday but is still a powerful, slow-moving system that meteorologists say could be devastating to Hawaii, a state that hasn't been pummeled by a hurricane in nearly a quarter-century.

"Hawaii is going to be impacted by Hurricane Lane. The question is how bad," Federal Emergency Management Agency administrator Brock Long said earlier in the week. On Friday, Long urged Hawaiians to heed warnings from emergency officials, and said that FEMA was prepared to provide food, water and shelter.

At 5 a.m. local time Friday (11 a.m. ET), Lane had maximum sustained winds of 110 mph. The hurricane's center was around 180 miles south of Honolulu, and was moving north at 5 mph toward Hawaii's main islands.

But the concern surrounding Lane is not about the winds; it's about the heavy rain.

"Excessive rainfall associated with this slow moving hurricane will continue to impact the Hawaiian Islands into the weekend, leading to catastrophic and life-threatening flash flooding and landslides," the National Weather Service said in its 11 a.m. ET bulletin, adding that tropical storm conditions were already thrashing the Big Island, Maui County and Oahu.

Hurricane-force winds were extending outward up to 35 miles from Lane's center with tropical-storm-force winds extending outward up to 140 miles, the weather service said.

Even if Lane does not make a direct hit on Hawaii, it could prove life-threatening.

"You don't have to have an actual landfall to have major problems," said NBC News' Al Roker. "It's still a dangerous storm, and it's not even close to being done yet."

The slow movement of the storm could mean that heavy rain and other effects are prolonged for Hawaii, officials said.

"Some weakening is forecast during the next 48 hours, but Lane is expected to remain a hurricane as it draws closer to the islands," the NWS said.

Hawaii County Civil Defense said heavy rainfall was already occurring on the Big Island, and flooding and landslides forced the closure of Highway 19 in Hilo and Honomu, as well as several other roadways, NBC affiliate KHNL of Honolulu reported.

Route 270 on the Big island was also closed due to landslides and flooding, the Hawaii Department of Transportation said.

The last Category 5 storm to even come close to Hawaii was Hurricane John in 1994, which skirted 345 miles south of the islands. The last severely damaging hurricane was Iniki, a Category 4 storm that killed six people in September 1992.

President Donald Trump on Wednesday issued an emergency declaration for Hawaii, which authorizes federal assistance to the region.

The president tweeted on Thursday: “Our teams are closely coordinating with the state and local authorities. You are in our thoughts!”

Hawaii County Managing Director Wil Okabe said five people were rescued from a flooded house in Hilo after a nearby gulch overflowed. No injuries were reported.

Although the ctr of #HurricaneLane will not make a direct hit over the islands at this time, we will still see heavy rain/large surf as the storm passes near the islands. As a Cat 3, we can already feel the strong wind on Oahu tonight. Please cont to take necessary precautions. pic.twitter.com/BzcXhJhg4p — Hawaiian Electric (@HwnElectric) August 24, 2018

United Airlines said it was canceling flights for Friday in and out of Kahului Airport on Maui due to weather conditions. It scheduled to additional flights from Honolulu to San Francisco on Thursday, and encouraged people who are traveling to or through affected areas to take advantage of policies where change fees and differences in fares are waived.

The storm brought with it the potential for large swells that could produce damaging surf along southern shorelines, and storm surge and large waves could raise water levels by 2 to 4 feet along south- and west-facing shores.

Most impressive flood video I've seen yet from Big Island of Hawaii. #HurricaneLane https://t.co/9sCCVlTKC6 — Bill Karins (@BillKarins) August 24, 2018

Counties in Hawaii have been opening shelters, although there have been fears that there are not enough, and some of those opened were not designed or reinforced to withstand forces greater than a tropical storm. However, officials have said they are safer alternatives for those in flood-prone areas, on ridge lines or in older homes with wood frames or single-wall construction.

Brad Kieserman, vice president for disaster operations for the American Red Cross, said "the state of Hawaii, the counties in Hawaii, and all of their partners have been planning for this type of event now for years."

He added: “Whether it makes landfall or not, it is a dangerous event, and we are ready for it.”