Radiation inversions are probably the most common type of temperature inversion. They form near the earth's surface during the night. After sunset, especially on a clear night the earth's surface cools because energy is radiated to space. The air which is just above the earth cools through contact with the cool surface. Air is a poor conductor of heat so only a thin suface layer of air is cooled leaving the air above almost unaffected and therefore warmer. Gentle breezes overnight can cause some mixing the air near the surface leading to the cool layer becoming slightly thicker as the night progresses. Some turbulence and reduced visibility can be evident below the inversion layer.