During a severe thunderstorm or hail storm, your first instinct is to hunker down and wait out the weather. However, if a tree or power line falls onto your home or building, you might be at risk of injury. Evacuate the building, find a safe place to gather, and call 911 and the local electric company if you notice downed power lines.
Until you can find a removal company to get the tree or power line off of your structure, stay away from the fallen object. In the interim, take pictures of the damage to submit to your insurance company. Once the tree is removed and your building is safe to reenter, you can take some immediate steps to prevent further damage, such as putting tarps over the damaged portion of your roof and placing containers to catch dripping water.