Fox News chief meteorologist Rick Reichmuth, talking Hurricane Dorian on "The Story with Martha MacCallum," said the storm now rolling toward Florida could drag on for as long as 10 days.

"It looks like the storm is going to begin to really slow down and its former progression, right now, it's moving about 30 miles an hour," Reichmuth told guest host Trace Gallagher on Thursday night.

"That might go down to like three or four miles an hour, and when that happens the rainfall totals are going to pile up and it's going to impact the area with really strong winds, the really heavy rain for a much longer time."

Dorian was churning over the warm, open waters of the Atlantic on Thursday. Forecasts showed it strengthening, the National Hurricane Center said it could hit Florida as a Category 4. That hurricane classification means sustained winds of 130-156 mph.

HURRICANE DORIAN'S PATH: WHAT YOU NEED TO KNOW

President Trump, adding his own alarm, warned that Dorian "will be BIG!"

The NHC said, as of 11 a.m. ET, that Dorian was a Category 1 storm with sustained winds near 85 mph. It was moving northwest at 13 mph. It was located about 220 miles north-northwest of San Juan, Puerto Rico.

Reichmuth did say other variables could help downgrade Dorian. For instance, he said, low pressure pulls up cooler water from deeper in the ocean, with the potential to "choke out the storm a little bit."

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Fox News' Travis Fedschun contributed to this report.