Welcoming the Dawn

My wife and I live in the centro, so it's bound to be noisier outside our apartment than in, say, San Felipe de Aguas (a beautiful suburb nestled among green hills just north of the city).

That said, can somebody please explain to me why there are firecrackers going off every day this month between 5:30 and 6:00 in the morning? Is there some Oaxacan-Christmastime-welcoming-the-dawn-festival about which I am completely unaware?