When you are in the storm, your health will start to deplete, and shields offer no protection.
As the game goes on, the safe zone on the map will shrink, and more of the island becomes covered by the storm. When you are in the storm, your health will start to deplete, and shields offer no protection. If you are staying on the outer reaches of the map, make sure you have a good idea of how long it will take you to reach the new safe zone once the next storm hits. The countdown timer will also give you ample warning to avoid any unwanted damage.