Subtropical Storm Alberto has gained an early jump on the 2018 hurricane season, heading toward expected landfall sometime Monday on the northern Gulf Coast, prompting thousands to evacuate.

Though the Atlantic hurricane season doesn't officially start until Friday, Alberto has become the first named storm this year, throwing disarray into long holiday weekend plans along Florida's Gulf Coast.

Franklin County, which is in the Florida Panhandle, issued mandatory evacuations for its barrier islands, Reuters reported. The evacuations affect about 4,200 homes.

The National Hurricane Center in Miami said at 2 a.m. EDT Monday that Alberto was maintaining its strength as it approached the Florida panhandle and was centered about 115 miles south-southwest of Panama City. The storm had maximum sustained winds of 65 mph as it approached the northern Gulf of Mexico.

"On the forecast track, the center of Alberto will move over the northern Gulf of Mexico tonight and cross the northern Gulf Coast in the warning area on Monday," the center said.

The center said a tropical storm warning is in effect from the Suwannee River in Florida to the Mississippi-Alabama state line. A tropical storm warning was discontinued from Florida's Anclote River to the Suwannee River.

A news release from Florida Gov. Rick Scott said that for Taylor County, "Voluntary evacuations have been issued for those in coastal zones and beach communities (Keaton, Dekel, Cedar, Dark Islands), mobile homes, RV parks and low-lying areas."

AL.com reported that double red flags are flying at beaches in Panama City and other areas, which means there are life-threatening rip currents.

"If you are planning to travel on Monday (Memorial Day) the combination of severe weather and heavy traffic conditions could prove hazardous. You are encouraged to plan accordingly," Gulf Shores officials said, according to the paper.

Fox News' Travis Fedschun and the Associated Press contributed to this report