What type of weather condition is generally associated with lower air density?

Lower air density is commonly associated with clear skies primarily due to the temperature and humidity factors involved. When skies are clear, there is typically less moisture in the air compared to overcast or stormy conditions. Dry air is less dense than humid air since water vapor is lighter than the oxygen and nitrogen molecules that make up the majority of the atmosphere.

In clear conditions, higher temperatures can also occur, which causes air to expand and further decreases its density. In contrast, as humidity increases during rainy or foggy weather, the air density tends to rise since moisture content replaces some of the heavier air molecules. Similarly, thunderstorms also involve significant moisture and turbulence, contributing to an increase in local air density variations. Thus, clear, dry conditions are well understood to correlate with lower air density.