When cooking up a very cold night, no matter the season, there are three major ingredients that need to be in play. A clear sky, dry air mass, and light winds are requisite for producing chills down your spine.

Typically when this type of pattern shapes up, a large dome of high pressure is centered right on top of your area. With a sinking motion under the high, clouds tend not to generate. Additionally, the pressure gradient looses up and allows the winds to go calm. Finally, as the high approaches from the west, around its clockwise flow, a northwest breeze sends in drier air, generally, unless you live on the west coast.

Lets go through the ingredients and see why each is important to for maximum cooling. A lack of cloud cover will allow any solar radiation that was absorbed by the ground during daylight hours to release and escape into space. In the event there where clouds around, clouds would absorb some of the radiation and send it right back to the ground, not allowing cooling to maximize.

To cool or even heat the air, energy is involved. The drier the air is, the less energy it takes for the air to cool or warm. Ideally a very dry air mass at night will cool quickly. During the summer when the dew point is in the upper 60’s and the sky is overcast, the mercury in your thermometer will drop slowly due to the abundance of moisture. Furthermore, this is the reason for a large range from the high and low temperature over arid (or desert) regions, due to a deficit in moisture.

The final ingredient incorporates the inactivity of wind. Since cold air is denser (“heavier”) then warm air, cold air will sink to lower elevations when the wind is calm. If there is wind present, the cold air will mix around and typically stick around higher elevated areas and not reach lower terrain.

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