WAVELAND, Miss. – When Hurricane Katrina’s punishing storm surge plowed ashore, it swamped seven of Coast Electric Power Association’s substations, vital to powering thousands of Mississippi homes and businesses. The facilities have long since been repaired, but a decade after the storm they remain at the same elevation, and just as vulnerable to catastrophic hurricanes.

Such storms are a growing threat. An Associated Press analysis of industry data found that severe weather is the leading cause of major outages on the nation’s power grid. The number of weather-related power outages has climbed over the last decade, with the greatest spikes in 2008 and 2011, according to the AP analysis and independent studies.

That leaves Coast Electric and other utilities across the country balancing customer costs with the need for improvements to counter the rising number of violent storms, floods and droughts threatening the U.S. power grid.

Katrina pummeled the Mississippi coast in August 2005, knocking out power to Coast Electric’s entire coverage area.

Facing sweltering summer heat and $110 million in damage, the small nonprofit cooperative focused on restoring power quickly, said vice president of engineering Scott Brown. The substations that flooded were repaired to pre-storm conditions – at the time, it would have been impractical to raise them or move them elsewhere.