Painting their towers during the day is probably the answer. Last overnight, WBZ was booming, as usual, here into Central Kentucky.
A couple of years ago, WSM in Nashville painted their tower and used their 5 KW backup and short auxillery tower during the day. During that time, they were not heard well outside of the Nashville metro area, but at sundown, they would light up the 50KW into their big tower until sunrise..... That lasted for a couple of weeks while their 800 foot tower was repainted.