It is common to think that the coldest temperature of the day occurs just before the sunrises. However it is normally right after sunrise that the coldest temp will occur if conditions are just perfect.
How does this happen? Going back to the basics, we gain heat from outsides sources the most important being the sun, while we also gain heat we also loose heat. It is a give and take.
However, during the night when we don't receive any solar radiation we still continue to loose it. During the day we receive solar energy but from sunset to sunrise we receive none, just some minimal amounts of other energy from other outside sources. This means we are consistently loosing, hence cooling.
As the sunrises the suns energy is so close to the ground and weak that we don't receive any the instant we start to see the light. It takes a bit of time before we stop continuously loosing and start regaining. At this point we begin the process of taking heat in again and the cycle initiates, hence beginning to warm. As a general rule the coldest time usually occurs about 30 minutes after sunrise on a picture perfect day (clear skies, light winds).
Of course many factors change when that coldest time will occur. Fronts, wind shifts and clouds play huge roles in temperatures. For example if clouds move in late, after midnight, more then likely the coldest temp will occur before the clouds or will drop much slower. Clouds act like a blanket; they help to keep the heat trapped in that we received during the day.
Meteorologist Kristen Connolly