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A depression strengthened into a tropical storm Saturday off the Carolinas, the latest wild weather to hit the nation over the long holiday weekend.

Tropical Storm Bonnie formed Saturday afternoon, the National Hurricane Center said just before 5 p.m. It was forecast to bring up to three inches of rain to the Carolinas, but rain had already started hitting the South Carolina coast earlier Saturday.

Whipping winds and dangerous waves as high as 13 feet could also could hit the two states, as well as Georgia and Florida over the coming days, forecasters said.

#Tropical Depression Two is pushing toward the Southeast coast. The potential impacts: https://t.co/wIX5WCT6Dd pic.twitter.com/QV267k2b1V — The Weather Channel (@weatherchannel) May 28, 2016

As of Saturday afternoon, no evacuations were ordered.

This NOAA satellite image taken Saturday, May 28, 2016 at 9:45 AMshows Tropical Depression Two continuing to move northwest towards the North and South Carolina coastline as it is expected to slightly strengthen into a weak tropical storm before making landfall. Elsewhere, a weak frontal boundary is draped across northern portions of New England, with thunderstorms beginning to develop across New York and Pennsylvania. A broad amount of cloud cover is also observed over the Midwestern United States with a north-south oriented frontal boundary. AP

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A depression becomes a tropical storm when winds reach 39 mph. Forecasters detected winds at 40 mph, making Bonnie the season's second-named tropical storm, four days before the official start of the Atlantic hurricane season.

Related: Two Dead in Texas As Plains Gear Up for More Bad Weather

Elsewhere in the nation, flooding and heavy rain were wreaking havoc. In Texas, at least two people were killed and four others were missing after torrential downpours, and the state was bracing for more rain through Memorial Day.

Washington County Judge John Brieden told The Associated Press that two drivers were missing. One was believed to have been swept out of the vehicle, while authorities feared the second motorist's car was submerged in flood waters. The incidents occurred in separate parts of the county, a rural area between Austin and Houston.

A man, foreground, checks to make sure everyone made it safely out of a truck that flooded when the three men in the background drove around a closed road barrier and lost control of the vehicle in rising flood water on May 27, 2016, in Magnolia, Texas. Michael Ciaglo / AP

Meanwhile, Travis County officials were searching for two residents who were swept away by the raging waters. Multiple people were rescued from rooftops by helicopters, Travis County Emergency Services tweeted Friday.

A fifth person, a child, was missing in Kansas. The 11-year-old boy fell into the fast-moving Gypsum Creek in Wichita and was swept away as friends tried to grab him, according to the Wichita Eagle.

In Tyler County, Texas, a mandatory evacuation was in place for the 30 to 40 homes in the Barlow Lake Estates subdivision, where rising crests could likely force the Corps of Engineers to release water from a local dam in the coming days, said county emergency management officials.

The resulting downstream flooding could be of historic proportions, county officials posted on Facebook.

Meanwhile, Missouri's governor declared a state of emergency ahead of expected heavy rains and warned that levees could be breached.

Related: Two Dead in Texas As Plains Gear Up for More Bad Weather

“Areas along the Missouri River and its tributaries in west-central Missouri are of particular concern because more rain could cause some levees to overtop,” Gov. Jay Nixon said in a statement issued on Friday evening.

Additional rainfall increases threat of deadly flooding. Remember, flooding kills more than any other #mowx threat: https://t.co/mSOkjSUqL2 — MO Public Safety (@MoPublicSafety) 28 May 2016

Since Tuesday, storms in the state have caused high winds, heavy rains and flash flooding — with more rain predicted into the weekend.

"State emergency management personnel will continue to work with local officials and law enforcement to assess and closely monitor the risk to the levees, and take appropriate action if needed,” Nixon said.

It doesn't take much water to make roads unsafe. Be alert when driving in flash flood areas. https://t.co/tmihGk20eL pic.twitter.com/0lC9J1FG6T — State of Missouri (@MoGov) 28 May 2016

The torrential downpour was part of severe weather that pummeled the nation's midsection Thursday night, with tornadoes reported in Kansas and Texas. More than 12 million people in the Plains were under flash flood watches Friday, and 1.4 million were under flash flood warnings, said TODAY's Al Roker.