Tropical Storm Beryl made landfall near Jacksonville, Fla. shortly after midnight on Monday with top winds of 70 miles an hour.
On land, the highest wind gusts were 73 mph in Mayport Fla. just east of Jacksonville.
Beryl is expected to dump about six inches of rain as it moves inland over the next couple of days in the southeast portion of the U.S., according to Navy hurricane specialist Dave Roberts at the National Hurricane Center.
Forecasters predict the storm surge and tide will cause significant coastal flooding in northeastern Florida, Georgia and southern South Carolina.
A tropical storm warning remained in effect early Monday for coastal areas of Florida and South Carolina, and it was expected to tangle holiday traffic after forcing the cancellation of some events and causing shoreline campers to pack up and head inland.
There have been many reports of trees and power lines down throughout the area, according to the National Weather Service.
The weather system is expected to continue dumping rain over parts of Florida and Georgia on Monday.
It is expected to weaken as it moves inland and become a tropical depression by Monday night, and then moves out to sea.
So far more than 20,000 people without power from Savannah, Ga. to Jacksonville and Daytona Beach, Fla.
Florida Gov. Rick Scott urged Florida residents in the affected areas to "stay alert and aware."
Beryl has already spoiled Memorial Day festivities for many and is expected to snarl traffic as the holiday weekend comes to a close. People visiting Cumberland Island, Ga. were ordered to leave ahead of the storm on Sunday afternoon. A jazz event was canceled Jacksonville, Fla.
This is the earliest since 1908 that two named storms have formed in the Atlantic Ocean. Tropical Storm Alberto was the first system to form earlier this month.
While the southeast is dealing with rain and high winds, the northeast dealt with a heat wave over the holiday weekend with temperatures in the mid 80s and 90s.
Over the weekend, almost 200 record highs reported around the country including 100 degrees in Tallahassee, Fla.
ABC News' Max Golembo and The Associated Press contributed to this report