The analysis uses data gathered from utility companies around the country and defines a major power outage as one impacting more than 50,000 customers. The criteria for a weather event vary from place to place. Climate Central finds that 58% of weather-related outages were caused by severe weather, such as high winds, rain, and thunderstorms. Another 22% is attributed to winter weather, 15% to hurricanes and tropical storms and a smaller number of outages could be attributed to extreme heat and wildfires.