Fast-moving Hurricane Helene was advancing Thursday across the Gulf of Mexico toward Florida, threatening an “unsurvivable” storm surge in northwestern parts of the state as well as damaging winds, rains and flash floods hundreds of miles inland across much of the southeastern U.S., forecasters said. The storm was upgraded to a Category 2 storm Thursday morning.

Landfall is expected by evening. The governors of Florida, Georgia, the Carolinas and Virginia have all declared emergencies in their states. In the Pacific, former Hurricane John strengthened Thursday morning back into a hurricane as it threatened areas of Mexico’s western coast with flash flooding and mudslides.

Meanwhile, Tropical Storm Isaac formed Wednesday in the Atlantic Ocean and was expected to strengthen as it moves eastward, possibly becoming a hurricane by the end of the week, forecasters said. Isaac was about 690 miles (1,115 kilometers) northeast of Bermuda with top sustained winds of 50 mph (85 kph), according to the U.S. National Hurricane Center in Miami. It was moving east at about 12 mph (19 kph).

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Here’s the latest:

John strengthens into a hurricane again near southwestern Mexico

MEXICO CITY — Former Hurricane John restrengthened into a hurricane on Thursday morning as it threatened areas of Mexico’s western coast with flash flooding and mudslides. Officials posted hurricane warnings for southwestern Mexico.

John hit the country’s southern Pacific coast late Monday, killing at least two people, triggering mudslides, and damaging homes and trees. It grew into a Category 3 hurricane in a matter of hours and made landfall east of Acapulco. It reemerged over the ocean after weakening inland.

Rain is falling and the roads are empty near where Helene is expected to make landfall

PANACEA, Fla. — Rain was beginning to blow in the predawn darkness Thursday along coastal U.S. Highway 98, which winds through countless fishing villages and vacation hideaways along Florida’s Big Bend.

Shuttered gas stations dotted the two-lane highway, their windows boarded up with plywood to protect against the storm. The road was largely empty at first light, with what drivers there mostly heading northeast, towards higher ground.

This stretch of Florida known as the Forgotten Coast has been largely spared by the widespread condo development and commercialization that dominates so many of Florida’s beach communities. The sparsely populated region is loved for its natural wonders — the vast stretches of salt marshes, tidal pools and barrier islands; the dwarf cypress trees of Tate’s Hell State Forest; and Wakulla Springs, considered one of the world’s largest and deepest freshwater springs.

Helene upgraded to Category 2 hurricane as it barrels toward Florida

MIAMI — Helene was upgraded Thursday morning to a Category 2 storm and is expected to be a major hurricane — meaning a Category 3 or higher — when it makes landfall on Florida’s northwestern coast Thursday evening.

As of early Thursday, hurricane warnings and flash flood warnings extended far beyond the coast up into south-central Georgia. The governors of Florida, Georgia, the Carolinas and Virginia have all declared emergencies in their states.

Tropical Storm Isaac forms in the Atlantic and is expected to strengthen, forecasters say

MIAMI — Tropical Storm Isaac formed Wednesday in the Atlantic Ocean and was expected to strengthen as it moves eastward, possibly becoming a hurricane by the end of the week, forecasters said.

Isaac was about 690 miles (1,115 kilometers) northeast of Bermuda with top sustained winds of 50 mph (85 kph), according to the U.S. National Hurricane Center in Miami. It was moving east at about 12 mph (19 kph).

Isaac is the ninth named storm in what is predicted to be a busy hurricane season, which runs from June 1 to Nov. 30 in the Atlantic. The National Oceanic and Atmospheric Administration predicts between 17 and 25 named storms, with as many as 13 hurricanes and four major hurricanes.

An average Atlantic hurricane season produces 14 named storms, seven of them hurricanes and three major hurricanes.