Transcript for Gulf Coast braces for storm surges over 10 feet from Hurricane Sally
Good evening and it's great to start another week with all of you at home. And as we come on the air tonight, two parts of this country are now dealing with weather emergencies. There is an urgent search right now for the missing in those wildfires and the uncomfortable exchange with the president today over climate change. But first, at this hour, hurricane Sally, upgraded to a category 2 hurricane late today, set to slam into the gulf coast. Now, this would be the third hurricane just this season alone to strike the gulf coast. It's a massive storm, winds already reaching 100 miles an hour, growing stronger over the warm waters of the gulf. Expects to move slowly once it hits, which is never good. The outer reaches of the storm dumping rain on south Florida. Flooding streets there. Washing over the sea wall in bay St. Louis, Mississippi and kicking up the waves and surf on dauphin island, Alabama. Mandatory evacuations in effect tonight. Let's get to the latest timing and track of this. Chief meteorologist ginger zee with us now. Reporter: David, we are 24 hours from this making landfall and you see that ridge behind me, we were thinking we could be life from dauphin island. We had to leave, because the causeway was already taking on water. That's how broad and impactful this will be for the next 48 hours. Let me take you to the map, because not only is the gulf of Mexico churning here, but it is moving west-northwest and it is slow. That slow movement is going to be key with this track as it makes landfall late tomorrow night into early Wednesday somewhere in eastern Mississippi along that Alabama state line. It's not the line of where the eye passes, it's that broad area that's going to be impacted from Pensacola, Florida, back to, say, slidell, New Orleans in a hurricane warning. And flash flood warnings go all the way to Birmingham, Alabama. You see, we stop the time there, David, Wednesday, midnight, rainfall and surge are going to be the biggest parts. We could end up with 15 to 20 inches of rain. I wish I could tell you this is going to scream out to the north after that, but it looks like a half foot of rain into Alabama. Ginger, thank you. As you heard ginger say, the right side of the hurricane, the dirty side of the hurricane can bring the worst effects. But the winds and the sheer amount of rain with this could be devastating. Senior meteorologist rob Marciano is in biloxi, Mississippi, where they are bracing for what's to come. Reporter: Tonight, hurricane Sally's strengthening surge. High water already flooding beach roads and hammering sea walls. The gulf coast bracing for a beast. These images just a taste of what's to come. The surge likely to be over ten feet in spots. It is anticipated that we could exceed 20 inches of rainfall. Reporter: Across Mississippi, we saw families boarding up homes, gassing up and filling sandbags any way they can. We met Wanda Daniels using a piece of tupperwear as a shovel, so, we helped her out. You are probably going to get flooded. Always do. When it rains heavy, I always get the water. Reporter: Officials racing to close flood Gates in Louisiana. I got a first-hand look at the massive flood wall outside new Orleans just a few weeks ago. And then there's this wall. New since Katrina, designed to keep any gulf surge out of the city. It is huge. 26 feet high and nearly two miles across. Power is going out right now. Reporter: Sally soaking Florida this weekend. Flooding streets with nearly a foot of rain. The powerful hurricane coming less than three weeks after Laura slammed ashore, turning a third of Louisiana into a disaster zone. All right, so, let's get to rob with us tonight, as well, and rob, I know the winds are always dangerous, the rain. But the storm surge is a real concern where you are tonight. Reporter: It certainly is, David. This area of the gulf so vulnerable in surge. Katrina brought a record 28-foot surge as a category 3. Sally a category 2. Look at the numbers. They may be conservative. We'll see six to at least 11 feet of surge, plus the rainfall that ginger mentioned, it's a slow mover. All right, this year, much like the year of Katrina is off the charts for activity. There are five named storms spinning at the same time in the that hasn't happened in 50 years, as we bear the brunt of this peak of a very active hurricane season. David? All right, rob Marciano and they're going to be on the scene for us throughout this. Rob, thank you.
This transcript has been automatically generated and may not be 100% accurate.