Hurricane Irma knocked out power to as many as 16 million people across the Southeast, according to recent estimates from utility companies. The vast majority of these outages occurred in the state of Florida, which was noticeably darker on satellite imagery as Irma pulled away from the state.
This imagery, courtesy of NOAA, shows data from the Suomi NPP satellite's VIIRS instrument, which has a special setting that helps scientists visualize nighttime lights. This "day-night band" can be used in a number of ways. Notably, it uses moonlight to help meteorologists track storm features when sunlight is absent. It also helps track changes in light emitted from Earth itself.
On the left is light emitted from Florida before Hurricane Irma (the night of May 11). On the right is what the VIIRS instrument saw around 3 a.m. Tuesday morning.
About 6.1 million customers (accounts) in Florida were without power on Monday afternoon, according to the Department of Energy. Translating that number to the actual number of people affected can be difficult. The energy companies directly track the number of meters that are "offline," but that doesn't say anything about how many people are impacted by that particular outage.
A Duke Energy spokeswoman said, per the latest Florida census data, a factor of 2.5 is a good estimate. In other words, for every account without power, 2.5 people are affected. Using that approximation, around 15.25 million people were without power in the state on Monday.
"We've never had that many outages. I don't think any utility in the country has," Eric Silagy, president and chief executive of Florida Power and Light — the state's largest electric utility — told The Washington Post.