at the crack of dawn
Very early in the morning, when the sun rises (dawn). It's a long drive, so we'll have to leave at the crack of dawn if we want to get there on time.
at the crack of dawn
and at the break of dawnFig. at the earliest light of the day. Jane was always awake at the crack of dawn. The birds start singing at the break of dawn.
at the crack of dawn
If you do something at the crack of dawn, you do it very early in the morning. I'm not used to getting up at the crack of dawn. We set off at the crack of dawn.