The Department of Transportation warned drivers on Monday not to get distracted by a rare, once-in-a-lifetime total solar eclipse that will be visible from more than a dozen states on August 21.

The department said the complete eclipse will be visible for millions of people coast to coast, “from Oregon to South Carolina.” And it will happen during the middle of the day, “when millions are on American roads, potentially causing one of the largest driver distractions in years.”