Harvey has dropped almost 52 inches of rain in Houston. Here's where it's moving next.

Doyle Rice

Tropical Storm Harvey has broken the all-time contiguous U.S. rainfall record from a tropical storm or hurricane, the National Weather Service said Tuesday.

East of Highlands, the Cedar Bayou gauge has picked up 51.88 inches of rain from Harvey, the weather service said. This broke the record of 48 inches set in Medina, Texas, from Amelia in 1978.

It's just under the all-time U.S. rainfall record from a tropical cyclone, which was 52 inches in Hawaii from Hurricane Hiki in 1950.

On Tuesday night, Harvey was 85 miles south of Port Arthur, Texas, and 85 miles south by southwest of Cameron, La., and was moving east at 6 mph, according to the National Hurricane Center. 

It will make a final landfall somewhere near the Texas/Louisiana border, likely early Wednesday.

Harvey is then expected to slowly move northeast across Louisiana and Arkansas as a tropical depression from Thursday into Saturday.

As it spins offshore, the storm is expected to dump an additional 6 to 12 inches of rain through Friday over the upper Texas coast and into southwestern Louisiana, exacerbating the life-threatening, catastrophic flooding in the Houston area, the hurricane center said.

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As of Tuesday afternoon, up to 30% of Harris County is under water, a flood official said. Harris County is home to 4 million people, making it the third-largest county in the U.S.

Amazingly, over 6 million Texans have been impacted by 30 inches or more of rain since Friday, the weather service said.

Brief tornadoes may also form anywhere from Galveston eastward to just south of New Orleans, the National Weather Service warned.

As of 4 p.m. CDT, Harvey had maximum sustained winds of 50 mph with a few higher gusts reported. It was moving to the north-northeast at 6 mph.

Forecasters were also monitoring another system off the Carolina coast, which brought rain to the Mid-Atlantic on Tuesday. This system is forecast to race out to sea with minimal impact to the U.S.

Still another system is being watched in the eastern Atlantic Ocean, which has an 90% chance of becoming a tropical depression or storm in the next five days.