Hurricane Harvey could be the costliest natural disaster in U.S. history with a potential price tag of $160 billion, according to a preliminary estimate from private weather firm AccuWeather.

This is equal to the combined cost of Hurricanes Katrina and Sandy, and represents a 0.8% economic hit to the gross national product, AccuWeather said.

“Parts of Houston, the United States' fourth largest city, will be uninhabitable for weeks and possibly months due to water damage, mold, disease-ridden water and all that will follow this 1,000-year flood,” said AccuWeather president Joel Myers.

The Federal Reserve, major banks, insurance companies and other business leaders should begin to factor in the negative impact this catastrophe will have on business, corporate earnings and employment, Myers said.

Weatherwise, the worst is over in and around Houston, though catastrophic and life-threatening flooding from the rain that’s already fallen will continue for the rest of the week, the National Hurricane Center said.

As of 7 a.m. CDT, the center of Harvey was located 25 miles west-northwest of Lake Charles, La. Its maximum winds were 45 mph and it was moving to the north at 9 mph.

Though Harvey will slowly weaken into a depression as it tracks inland, it will still produce more rain – 3 to 6 inches from southwestern Louisiana up along the Arkansas/Mississippi border and into western Tennessee/Kentucky through Friday. Some areas could see as much as 10 inches of rain.

Flash flood watches are in effect for much of the Mississippi Valley due to the heavy rain threat.

"AccuWeather cautions that the negative impact from the storms are far from over. There will be more flooding, damage, fatalities and injuries," Myers said. "We urge all citizens near the path of Hurricane Harvey to remain vigilant and be prepared to take immediate action if flood waters rise."

The highest rainfall total from the storm so far is near Cedar Bayou, Texas, which registered 51.88 inches. This broke the contiguous-U.S. rainfall record for a tropical storm or hurricane, preliminary data from the National Weather Service show.