The agency said the season has the potential to become "extremely active", possibly the most active since 2010. They are calling for a total of 14 to 19 named storms, five to nine of them becoming hurricanes.
In its mid-season update, NOAA now predicts a higher likelihood of an above-average season.
Additional strengthening is expected, and Franklin is forecast to become a hurricane later today and reach the coast of Mexico as a hurricane tonight or early Thursday.
Earlier this year, NOAA scientists already predicted an above-average 2017 hurricane season.
The National Hurricane Center said satellite imagery has shown increased organization, which means Franklin is building its strength.
The National Hurricane Center in Miami upgraded the storm to a hurricane late Wednesday afternoon. An estimated $28.3 trillion worth of homes, businesses and infrastructure is vulnerable to hurricane strikes in the 18 U.S. Atlantic coastal states, according to the Insurance Information Institute in NY.More news: Why is Mayweather playing the underdog against McGregor?
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An average hurricane season produces 12 storms between June 1 to November 30.
Nearly 25 years have passed since a Category 5 hurricane struck south of Miami, and the city's vulnerability to catastrophic storm damage has grown exponentially, according to a new insurance underwriters' analysis. Cindy made landfall on June 22 at the Louisiana-Texas border and caused heavy rain, inland flooding and multiple tornado outbreaks.
And the three-month period ahead is when the vast majority of storms - about 95 percent - occur. It was moving to the west at 12 mph and was located 105 miles east-northeast of Veracruz, Mexico.
Peak season for activity has historically been from mid-August through October, NOAA said.
Wednesday's update decreases the chance of a near normal season from 35 to 30 percent, and a below normal season from 20 to just 10 percent.