Hurricane Helene is steadily gaining strength and is poised to bolt through the Gulf of Mexico before striking northern Florida late Thursday. The storm is forecast to intensify into a large and extremely dangerous Category 4 hurricane before coming ashore near where the Panhandle meets the state’s Big Bend area.

Because of its unusual size, hurricane and tropical storm alerts cover the Florida Peninsula and most of the Panhandle and extend through Georgia, South Carolina and western North Carolina.

Rounds of rain will begin to surge north over Florida on Wednesday while coastal flooding increases along its western shores.

Tropical-storm-force winds should reach the Florida Peninsula by Wednesday afternoon or Wednesday night. Conditions will rapidly deteriorate Thursday into Friday as the storm makes landfall and plows inland.

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In the predicted landfall zone to the northeast of Apalachicola on Apalachee Bay, sustained winds could reach 100 mph with gusts up to 110 to 140 mph during the second half of Thursday. The storm surge, or rise in ocean water above normally dry land, could reach 15 to 20 feet in the Big Bend area, or just to the east and south of where landfall occurs. The National Hurricane Center is describing this surge as “catastrophic and deadly.” This zone could also see 10 to 12 inches of rain.

The storm’s size and strength mean it could produce serious impacts in major population centers from Tampa to Atlanta to Nashville. Particularly dangerous amounts of rain are forecast in the southern Appalachians that “will likely inundate communities in its path with flash floods, landslides, and cause extensive river and stream flooding,” the National Weather Service wrote.

Here are forecasts for 11 cities near its path:

Tampa: Tropical storm and storm surge warning, flood watch

Depending on the storm’s track, Tampa might end up to the south and east of the most severe wind and rain impacts, but it could still see a period of hazardous conditions. Significantly, Tampa faces a potential ocean surge of 5 to 8 feet, which would produce the most serious inundation of low-lying areas since the 1980s.

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Time period of concern: Wednesday night to Friday, with the worst expected Thursday.

Peak gusts: 65 to 85 mph, strongest near shore.

How much rain: 3½ to 6 inches, most near shore.

Flood risk: Level 2 out of 4.

Orlando: Tropical storm warning

Orlando could see periodic downpours starting Wednesday afternoon and continuing through Thursday. The heaviest rain and strong winds may come through Thursday afternoon.

Time period of concern: Wednesday to Thursday night, with the worst Thursday afternoon.

Peak gusts: 40 to 60 mph.

How much rain: 1 to 3 inches.

Flood risk: Level 1 out of 4.

Gainesville, Fla.: Tropical storm warning, flood watch

Showers and storms become likely by late Wednesday. The strongest winds and most torrential downpours should come late Thursday.

Time period of concern: Wednesday night to Friday morning, worst second half of Thursday.

Peak winds: 50 to 70 mph.

How much rain: 2 to 4 inches.

Flood risk: Level 2 of 4.

Panama City, Fla.: Tropical storm warning, flood watch

Showers begin Wednesday with rain intensity peaking as the storm center makes its closest approach Thursday, when some flooding is possible. Because the center will pass to its east, the worst of the ocean surge should miss the area, but water levels could still rise 1 to 3 feet.

Time period of concern: Wednesday night through Friday morning, worst Thursday night.

Peak gusts: 40 to 60 mph.

How much rain: 3 to 5 inches, less west and more east.

Flood risk: Level 3 of 4.

Tallahassee: Hurricane warning, flood watch

Unless Helene’s track shifts, serious impacts are likely as the storm’s core is projected to move over the area, bringing the possibility of damaging winds, widespread power outages and flash flooding.

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Time period of concern: Wednesday night through Friday morning, worst late Thursday.

Peak gusts: 75 to 120 mph.

How much rain: 6 to 8 inches.

Flood risk: Level 3 of 4.

Savannah, Ga.: Tropical storm warning

Tropical storm conditions could occur as far east as Savannah, where periodic gusty downpours are probable as the storm’s outer rain bands circulate northward. Some of these rain bands could produce tornadoes, and the National Weather Service has placed the area in a Level 3 out of 5 risk zone for severe storms.

Time period of concern: Thursday and Friday.

Peak gusts: Around 40 mph.

How much rain: 2 to 4 inches.

Flood risk: Level 2 of 4.

Macon, Ga.: Hurricane warning and flood watch

Macon could be on the front line of inland cities that experience significant impacts from Helene. A period of damaging winds that produce downed trees and power outages and flash flooding are possible.

Time period of concern: Wednesday night through Friday, worst Thursday night and early Friday.

Peak gusts: 70 to 90 mph.

How much rain: 7 to 10 inches.

Flood risk: Level 3 of 4.

Atlanta: Tropical storm warning and flood watch

In its discussion early Wednesday, the local Weather Service office for Atlanta warned that “a significant rainfall event is expected.” Substantial flash flooding is feared, as some spots may see double-digit rainfall totals. Strong winds combined with saturated soils could result in downed trees and power outages in widespread areas.

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Time period of concern: Thursday through Friday, worst early Friday.

Peak gusts: 45 to 70 mph.

How much rain: 8 to 10 inches.

Flood risk: Level 3 of 4.

Charlotte: Tropical storm warning

Charlotte might end up far enough east of the storm’s track to see more benign impacts compared with locations to the south and west. A period of heavy rain and stronger winds could, however, produce inclement conditions for the Friday morning commute.

Time period of concern: Thursday through Friday, worst first half of Friday.

Peak gusts: 40 to 55 mph.

How much rain: 2 to 4 inches.

Flood risk: Level 2 of 4.

Asheville, N.C.: Tropical storm warning and flood watch

The local Weather Service office anticipates the heaviest rainfall rates Thursday night and Friday morning, “on top of already saturated soils.” Flash flooding is forecast to be widespread, and the Weather Service is warning of “locally severe and life-threatening flooding.”

Time period of concern: Wednesday through Friday, worst Thursday night to early Friday.

Peak gusts: 50 mph.

How much rain: 6 to 10 inches.

Flood risk: Level 4 of 4.

Nashville

The remnant center of Helene is forecast to pass rather close to the city Friday. By then, the wind threat will be minimal, but Nashville could pick up enough rain for areas of flooding.

Time period of concern: Late Thursday into the weekend, worst Friday.

Peak gusts: 30 mph.

How much rain: 4 to 5 inches.

Flood risk: Level 2 of 4.