During power outage like in tornado or storm, how can I comfort my toddler when I am scared to death myself?

Be there for them. First, have a plan. If there's a plan, you'll be less scared (i have flashlights, and know where the matches are, and there are strategically placed candles, etc). Then you have something to do, and that helps. If your toddler sees you doing things, they may want to help. It can be tremendously hard to remain calm, but as a parent, you have to remember you're there to protect them.