(CNN) Joaquin strengthened into a major hurricane on Wednesday night, the U.S. National Hurricane Center announced.

The Category 3 storm is poised to pound the Bahamas with heavy rain and dangerous storm surges.

And the storm's movement later this week could have flooding implications for an already drenched eastern United States . While forecasters are having a hard time figuring where Joaquin is headed, they believe the storm will continue to strengthen over the next day or so.

Joaquin's outer bands were already splattering the southern Bahamas and Cuba with rain Wednesday night.

The storm's center was spinning 170 miles (275 kilometers) east of the central Bahamas. Its maximum sustained winds of 115 mph (185 kph) extended 35 miles (56 kilometers) from the eye. Tropical storm force winds reached farther, up to 140 miles (220 kilometers) from the center.

A radar image of Hurricane Joaquin at 8:30 p.m. ET Wednesday.

A hurricane warning was in effect for the central and northwestern Bahamas, with the storm's center expected to be near or over the islands by Thursday before turning north, the hurricane center said.

More than 10,000 people live on the Bahamian islands most squarely in the storm's path. Ten to 15 inches of rain could fall over much of the central Bahamas through Friday, with lesser amounts expected over the rest of the country, the center said. Isolated amounts could reach 20 inches.

"Winds are expected to first reach tropical storm strength in the warning area Wednesday night, making outside preparations difficult or dangerous," the hurricane center said about the Bahamas. "Preparations to protect life and property should be rushed to completion."

Rain and winds aren't the only concerns: Dangerous storm surges -- with water levels as high as 3 to 5 feet above normal tides -- are possible on the Bahamian coasts.

Swells from Joaquin also will affect the southeastern U.S. coast by Thursday, potentially creating life-threatening rip currents, the hurricane center said.

A U.S. landfall?

A hurricane hasn't made landfall in the eastern United States since Hurricane Arthur hit North Carolina in 2014. That could change with Joaquin.

Forecasters expect Joaquin to turn north after the Bahamas, but they have low confidence in predicting the path after that. Many U.S. computer forecast models predict a hit on the East Coast next week, anywhere from the Carolinas to more northern Mid-Alantic states.

One European-based model predicts the storm going out to sea instead.

"Anywhere from South Carolina all the way up to the Northeast needs to be on the lookout for this storm," CNN meteorologist Jennifer Gray said. "There's still a lot of uncertainty with this storm."

Computer models predict different paths for the hurricane.

Gray said a low pressure system over the Southeast could influence how Joaquin travels northward.

Significant rain possible for Mid-Atlantic next week

Photos: Devastating hurricanes of the last 30 years Photos: Devastating hurricanes of the last 30 years The last 30 years have brought plenty of deadly and destructive storms to the United States, including 2005's Hurricane Katrina (here, police and others use boats to rescue people in a flooded New Orleans neighborhood). Click through the gallery to see more photos of disastrous hurricanes over the last three decades, and check out this video to find out which states have been hit the most often. Hide Caption 1 of 23 Photos: Devastating hurricanes of the last 30 years Hide Caption 2 of 23 Photos: Devastating hurricanes of the last 30 years Sandy, 2012: It technically lost its hurricane status shortly before striking New Jersey, but its gigantic size -- it covered 1.8 million square miles at landfall -- sent devastating storm surges to the coast. Here, a man looks for pieces of his beach house after It technically lost its hurricane status shortly before striking New Jersey, but its gigantic size -- it covered 1.8 million square miles at landfall -- sent devastating storm surges to the coast. Here, a man looks for pieces of his beach house after Sandy demolished it in Seaside Heights, New Jersey. With 72 directly killed in eight states, this was the most deadly tropical cyclone outside the South since 1972's Hurricane Agnes. At least 650,000 U.S. homes were damaged or destroyed in the U.S. Hide Caption 3 of 23 Photos: Devastating hurricanes of the last 30 years Hide Caption 4 of 23 Photos: Devastating hurricanes of the last 30 years Irene, 2011: After hitting North Carolina, After hitting North Carolina, Irene did most of its damage in the way of heavy rain and flooding in New York and New England. In southern Vermont alone, nearly 2,400 roads were damaged or destroyed, NOAA says. Here, Tony Carr carries a TV set September 1 from his home, which was destroyed by Irene-related floods in Prattsville, New York. Hide Caption 5 of 23 Photos: Devastating hurricanes of the last 30 years Hide Caption 6 of 23 Photos: Devastating hurricanes of the last 30 years Ike, 2008: After killing scores in the Caribbean, Ike turned to Texas, sending storm surges that leveled homes on Galveston Island. It's remnants did extensive damage as far north as Ohio, where 2.6 million people lost power. Here, an Air Force Reserve pararescueman scans the ravaged Texas landscape shortly after Ike. Hide Caption 7 of 23 Photos: Devastating hurricanes of the last 30 years Hide Caption 8 of 23 Photos: Devastating hurricanes of the last 30 years Katrina, 2005: Unforgettable Unforgettable Katrina -- the costliest hurricane and one of the five deadliest to hit the United States, according to NOAA -- devastated the Gulf Coast days after crossing Florida. Flooding destroyed thousands of homes in the New Orleans area alone; storm surges wiped out coastal towns in Mississippi. Here, people stand stranded on a roof in New Orleans. Hide Caption 9 of 23 Photos: Devastating hurricanes of the last 30 years Hide Caption 10 of 23 Photos: Devastating hurricanes of the last 30 years Rita, 2005: Just a month after Katrina, : Just a month after Katrina, Hurricane Rita piled on, slamming into the Louisiana coast. Wind, rain and tornadoes left billions in damages from eastern Texas to Alabama. Here, surging water from Rita reach the streets of New Orleans' Ninth Ward, topping a levee that had just been patched after Katrina damaged it. Hide Caption 11 of 23 Photos: Devastating hurricanes of the last 30 years Hide Caption 12 of 23 Photos: Devastating hurricanes of the last 30 years Wilma, 2005: The year might be remembered for the one-two punch of Katrina and Rita, but : The year might be remembered for the one-two punch of Katrina and Rita, but Wilma , which hit Florida after devastating Mexico's Yucatan Peninsula, would become (as of May 2015) the U.S.'s fifth most costly cyclone. Here, workers remove debris from a Miami flower and plant shop on October 28. Millions were without power in the state. Hide Caption 13 of 23 Photos: Devastating hurricanes of the last 30 years Hide Caption 14 of 23 Photos: Devastating hurricanes of the last 30 years Beta, 2005: Beta wasn't one of the most devastating cyclones, but we include it here to make a point: There were so many named storms in the Atlantic in 2005 that forecasters' pre-approved 21-name list for the year was exhausted. So they went to the Greek alphabet six times, including for Hurricane Beta, which directly hit part of Nicaragua. Here, people wade through a street flooded by Beta in Honduras on October 30. Hide Caption 15 of 23 Photos: Devastating hurricanes of the last 30 years Hide Caption 16 of 23 Photos: Devastating hurricanes of the last 30 years Ivan, 2004: This year also was hurricane-heavy, punctuated by : This year also was hurricane-heavy, punctuated by Ivan , a storm with two lives. First, it killed dozens in the Caribbean and slammed into Alabama. Later, its remnants went back over Florida from the Atlantic and re-formed in the Gulf as a tropical storm, making another landfall in southwestern Louisiana. It spawned more than 100 tornadoes, one of the factors that left considerable damage across the Southeast and some mid-Atlantic states. Here, a woman walks over debris as she visits her home, destroyed by Ivan, in Perdido Key, Florida, on September 20. Hide Caption 17 of 23 Photos: Devastating hurricanes of the last 30 years Hide Caption 18 of 23 Photos: Devastating hurricanes of the last 30 years Floyd, 1999: Deadly flooding, especially in North Carolina, was one of Floyd's main legacies. Parts of eastern North Carolina and Virginia received 15 to 20 inches of rain, and flooding led to the razing of thousands of buildings -- most of them homes -- from North Carolina to New Jersey. At the time, it was the deadliest U.S. hurricane since 1972. Here,a beach house, severely damaged by Floyd, sits crumbled sits in the sand on the Oak Island town of Long Beach, North Carolina, on November 10. Hide Caption 19 of 23 Photos: Devastating hurricanes of the last 30 years Hide Caption 20 of 23 Photos: Devastating hurricanes of the last 30 years Andrew, 1992: Andrew blasted its way across south Florida on August 24 as a Category 4 with peak gusts measured at 164 mph. After raking entire neighborhoods in an around Homestead, it moved across the Gulf to hit Louisiana as a Category 3. It was responsible for 23 U.S. deaths and three in the Bahamas. Here, a sailboat sits on a sidewalk at Dinner Key in Miami after Andrew washed it ashore. Hide Caption 21 of 23 Photos: Devastating hurricanes of the last 30 years Hide Caption 22 of 23 Photos: Devastating hurricanes of the last 30 years Hugo, 1989: Hugo ripped through the Carolinas, starting with Charleston, South Carolina, on September 22 as a Category 4 after raking the U.S. Virgin Islands and Puerto Rico. Here, a man stands in a destroyed house on September 27 in South Carolina. Hide Caption 23 of 23

Landfall or not, Joaquin at the very least could send significant rainfall to the East Coast, where some states already were dealing with flood threats from separate systems this week.

"There is so much tropical moisture, we will get 10 inches of rainfall in the Mid-Atlantic (in the next seven days) -- and that's with a miss," CNN meteorologist Chad Myers said. "If we get a hit ... that number may double."

Heavy rains hit the Mid-Atlantic and New England this week, and 2 to 6 inches of rain were still expected to fall in New England on Wednesday.

Large portions of Vermont, New Hampshire and Maine were under flood watches or warnings Wednesday afternoon.

Flooding made some streets impassable in Portland, Maine. Several cars were stalled on one street there after their drivers tried to drive through standing water, CNN affiliate WMTW reported