Why is there sometimes no frost on cold mornings?
Wind speed plays a major role in frost development. When the winds are calm (or very light) and temperatures are cold enough, frost is likely. Clear skies also contribute to frost development. Note that air temperatures don't have to be at or below freezing for frost development. The surface temperature of your vehicle may be much lower than the air temperature. Humidity levels also play a role. The bottom line is that even though it may be very cold in the morning, strong winds will prevent frost from developing