First Swell Early swell, bud brown, no color. First Leaf One leaf out at 90 to the stem. Fourth Leaf Four leaves out at 90 to the stem. Cooling of the ground by radiation of heat to the open sky causes radiation freezes. The movement of a cold area mass into the area causes advective freezes.
Clouds help to hold in the day's heat and keep the morning temperatures warmer.
Winds mix warmer air with cold air next to the ground. I near worry too much if the forecast is for cloudy windy conditions. The dew point is very important but hard to determine since the weather service no longer gives that information. The dew point is the temperature at which the air is saturated with water vapor. The temperature will fall faster in dry air than moist air.