Helene became a hurricane Wednesday after the huge storm rapidly strengthened in the Caribbean Sea and moved north along Mexico's coast on a path toward the U.S., leading residents to evacuate, schools to close, and officials to declare emergencies in Florida and Georgia. The storm's center was near Mexico's Yucatan Peninsula on Wednesday, the U.S. National Hurricane Center said, and it was expected to intensify and grow in size as it crosses the Gulf of Mexico. Heavy rainfall was forecast for the southeastern U.S. starting Wednesday, with a life-threatening storm surge along the entire west coast of Florida, according to the center. The storm is so large that areas roughly 90 miles (145 kilometers) north of the Georgia-Florida line could expect hurricane conditions. States as far inland as Tennessee, Kentucky and Indiana could see rainfall. On Wednesday morning, winds of tropical storm force, at least 39 mph (62 kph), extended as far as 275 miles (445 kilometers) from Helene's center. “You are going to have a major hurricane plowing inland, and storms take a little time to decay once they’re inland,” said Brian McNoldy, an environmental researcher at the University of Miami. Forecasters warned of possible tornadoes Wednesday night in western Florida and southern Alabama and said the tornado risk would increase Thursday, expanding across Florida and into Georgia and South Carolina. Helene is expected to become a major hurricane — a Category 3 or higher, with winds above 110 mph (177 kph) — on Thursday, the day it's set to reach Florida's Gulf Coast, according to the hurricane center. The center issued hurricane warnings for part of Mexico’s Yucatan Peninsula and Florida's northwestern coastline, where large storm surges of up to 15 feet (4.5 meters) were expected. As residents of Florida’s Big Bend — the curving stretch of Gulf coastline in the state's north — battened down their homes, many saw the ghost of 2018's Hurricane Michael. That storm rapidly intensified and crashed ashore as a Category 5 that laid waste to Panama City and parts of the rural Panhandle. “People are taking heed and hightailing it out of there for higher ground,” said Kristin Korinko, a Tallahassee resident who serves as the commodore of the Shell Point Sailboard Club, on the Gulf Coast about 30 miles (48 kilometers) south of the state capital. In Tallahassee, where stations had started to run out of gas, 19-year-old at Florida A&M student Kameron Benjamin filled sandbags with his roommate to protect their apartment before evacuating. Their school and Florida State shut down ahead of the storm. “This hurricane is heading straight to Tallahassee, so I really don’t know what to expect," Benjamin said. In the Pacific, former Hurricane John re-formed as a tropical storm Wednesday and threatened areas of Mexico's western coast anew. John had hit the country's southern Pacific coast late Monday, killing two people, blowing tin roofs off houses, triggering mudslides and toppling scores of trees, officials said Tuesday. It grew into a Category 3 hurricane in a matter of hours and made landfall about 80 miles (128 kilometers) east of the resort city of Acapulco. It weakened after moving inland but later reemerged over the ocean. On Wednesday, officials issued a hurricane watch for the coast from Acapulco to Zihuatanejo and tropical storm warnings from Punta Maldonado to Lazaro Cardenas. John was about 110 miles (180 kilometers) southwest of Acapulco with maximum sustained winds of 40 mph (65 kph) and was moving east at 2 mph (4 kph). Helene, which formed Tuesday in the Caribbean, is expected to move over deep, warm waters, fueling its intensification. The hurricane was about 500 miles (810 kilometers) southwest of Tampa, Florida, and had top sustained winds of 80 mph (130 kph), according to the hurricane center. Forecasters said it is expected to become a major hurricane with its center making landfall in the Big Bend area of Florida’s northwestern coast as soon as late Thursday. Mara Lezama, the governor of the coastal Mexican state of Quintana Roo, shared photos of rain-swept streets. In Cancun, heavy waves threatened to worsen the resort city's problem with beach erosion. In western Cuba, authorities moved cattle to higher ground and medical brigades were dispatched to communities usually cut off by storms. The government preventively shut off power in some communities as waves as high as 16 feet (5 meters) slammed into Cortes Bay. The Cayman Islands began recovering after heavy rains and big waves lashed them Tuesday. Schools remained closed Wednesday as flood warnings continued and residents pumped water out of their flooded homes. Tropical storm warnings were in effect for the upper Florida Keys, southern Florida and the state's northeast coast and were extended northward Wednesday morning to Altamaha Sound, Georgia.