The northern eyewall of “extremely dangerous” Hurricane Laura has moved over Louisiana’s Cameron Parish,  bringing a “catastrophic storm surge, extreme winds and flash flooding” to southwestern Louisiana, the National Hurricane Center said. The storm intensified rapidly into a Category 4 hurricane as it barreled toward the Louisiana and Texas coasts and was on the verge of becoming a Category 5 — the hurricane center’s most powerful classification.

Laura was packing 150 mph sustained winds. It could cross the threshold into a Category 5 at the 157 mph mark.

Laura is expected to be the strongest hurricane to hit the U.S. this year. At least 20 million people are in its path and more than half a million have been ordered to evacuate.