On the East and Gulf Coast areas, there are thousands of incidents of daytimers running all night and directional stations going non-directional during hurricanes. Similar cases, although less frequent, have been heard for tornado situations, major floods, extreme storms and other disasters.
As long as those situations are not commercialized, it is permitted. Almost any reasonable explanation has seemed to be valid over the decades.
Few stations have equipment that allows raising the power, although there have been many, many of the ones I described where a station has remained on day power at night and operated non-directionally.
One of the stations that has given great service during hurricanes is the 50 kw 690 AM station in Jacksonville. During many Atlantic hurricanes, from Miami up to the Carolinas, it has remained on the air all night with the daytime non-directional facility to give emergency information.