Under conditions of high pressure, the heated air will not continue to rise. Being cooler than the surrounding air, it will not rise. High pressure leads to stable air conditions. When the ground is heated, the air will not rise. If air does not rise, rain cannot condense.
Convection rain requires a warm ground and low pressure.
It causes short showers interspaced with sunny periods. The rain is caused by rapidly forming Cumulus and Cumulonimbus clouds. It tends to occur in the later part of the day or early evening. Because land warms faster than the sea, this type of rain is far more common over land. Convection causes fluffy Cumulus clouds to appear over land when the nearby sea is cloudless.