Hurricane Irma became tied for the seventh strongest storm to make landfall in U.S. history by a key measurement of atmospheric pressure.
Hurricane Irma made landfall at Cudjoe Key at 9:10 a.m. with a minimum central pressure of 929 millibars. Atmospheric pressure is one of the major measurements meteorologists use to describe storms. The lower the pressure, the stronger the storm.
Only six storms on record had lower pressures when striking the United States, including Katrina. When Katrina hit in 2005, it had lower pressure but its wind speed kept it at Category 3.
The 929 pressure mark ties Irma with the deadly 1928 Lake Okeechobee hurricane.
Irma's arrival also marks another first.
Colorado State University hurricane researcher Phil Klotzbach says this is the first year on record that the United States has been hit by two storms that were Category 4 upon landfall: Harvey and Irma.