Tropical Storm Isaac lashed the Florida Keys and headed towards the northern Gulf Coast, prompting officials in Florida, Louisiana, Mississippi and Alabama to declare states of emergency.
The Vampire Diaries star had been planning to travel to Louisiana in aid of his non-profit organisation the Ian Somerhalder Foundation (ISF), which he set up to raise awareness of environmental issues - but the bad weather affected his trip.
In a post on his Twitter.com page, Somerhalder writes, "Damn hurricane get'n (getting) in the way of me going down to Louisiana to fight to preserve the ISFsanctuary land from be'n (being) destroyed by a development."
Jason Alexander also took to his account on the microblogging site to tell followers his elderly mother was in storm-lashed Florida - but was confident she would be fine.
He joked, "My 92 year old mommy is in the middle of the Florida hurricane. She's a tough bird. I wouldn't bet on the hurricane."
The storm, which is predicted to turn into a hurricane by Tuesday (28Aug12), comes seven years to the week that Hurricane Katrina destroyed large parts of New Orleans in Louisiana, and rapper Meek Mill has urged his followers to stay safe.
He adds, "7 years ago, New Orleans was hit by Hurricane Katrina. Today, Hurricane Issac is headed their way. PLEASE PRAY. R-T (re-tweet) TO GET THE WORD OUT."