During the day, the surface of the Earth heats up because of solar radiation. In warmer air, the vertical movement of the air parcels intensifies. This means that the warm air mixes in a thicker layer than in colder air. Due to the intensive mixing processes, convective turbulence can often be expected on warm days.

At night or in the winter, the extent of the friction layer decreases as the surface of the Earth cools (the atmosphere is more dense). Consequently, the intensity of the convection and the surface wind decreases Its minimum value is to be observed around sunrise.

Note: Thermal turbulence is greatest around 1500 h on clear sunny days (when the highest temperatures are reached) - In weather conditions when thermal activity can be expected, many pilots prefer to fly in the early morning or in the evening when the thermal activity is not as severe.