"Temperaturile au scăzut azi-noapte."
Translation:The temperatures fell last night.
In a 24 hours day, the first hours starting from 00:00 are night hours. Then comes the daylight, when we talk about "azi-noapte" meaning the last night in chronological order, which is part of today. Which is not yesterday night (that would be "ieri-noapte"), although it started yesterday in the evening (before 00:00).