1. Be prepared with alternative lighting. Have a flashlight and extra batteries somewhere that's easily accessible so you won't be fumbling in the dark.
2. If you don't have coolers and extra ice on hand, you have a limited time to enjoy perishable food. Once the temperature in your fridge goes above 40 degrees Fahrenheit, it's time to throw things away. Bacteria will start to grow, and you don't want to have to clean out rotten or melted food days later.
3. Turn off or disconnect appliances. A momentary power "surge" can damage computers and other devices. If it's hot out, you'll need to turn off your air conditioner so that when power does return, thousands of air conditioners starting up at the same time don't cause another outage.
4. In the meantime, keep yourself and your house cooler by opening all your windows, including the vent in your attic. Pull down shades on the south and west sides to keep the sun from making things hotter. Move to the lowest level of your home, wear light clothing, and stay hydrated.
5. If you lose power in cold weather, layer up. Never use your oven as a source of heat and never burn charcoal indoors. If the power could be out for a long period of time, plan to go to the home or a friend or relative, or a public space that has heat to keep warm.
You can't control the weather or your city's power grid, but you can be prepared for a blackout with equipment and knowledge.