There are dramatic things that lead to power outages: exploding substations, ice storms that paralyze the entire East Coast, and heatwaves devour the country and represent an enormous burden on the electricity network by air conditioning systems. Then there are the less dramatic sources, such as squirrels.
Although customers for clients, a flood or a massive storm will usually hit the highest number of people in terms of actual power interruption events (regardless of magnitude), no storm can hold a candle against the squirrels' antics.
The cute and furry, but terribly destructive little creatures love to use power lines as their personal highways. The leashes are tall, comfortable and provide safe routes across roads near trees and rooflines that carry groceries. All places that squirrels love. Of course, this would not be a problem except that squirrels are so long that their bodies can easily bridge the space between wires, transformer components and other parts of the power grid that can lead to a short circuit.
Under Ideal Under certain circumstances, electric shock ejects the squirrel's body from the device (and resumes current flow). However, in many cases, the body of the squirrel remains stuck in the device and triggers a persistent fault in which circuit breakers and nearby devices are blown. The squirrel problem is so grave that many utility companies have resorted to the installation of squirrel deterrents, including the means typical of bird feeding troughs (rotating baffles, cans to cover sensitive areas on mast and transformer, and even the use of predatorine to keep squirrels from climbing particularly heavily hit Poland and substations).