One factor that helps to contribute to instability is the uneven heating of the ground. A southerly wind can also contribute to instability. This wind can increase the dew point, and when you increase the dew point you create a higher latent heat. Unstable air is what helps to create thunderstorms . If there is a greater dew point there is more water vapor.
Water vapor plays a great role in instability.
If there is more water vapor there are more thunderstorms. Evaporation occurs when water changes, for every gram there is a tremendous amount of cooling. It is associated with latent heat. Condensation does the opposite. Moisture condenses, heat lets out in the atmosphere.