There is a negative relationship between rainfall and pressure. When the air pressure is lower then more rainfall occurs and when the pressure is higher then less rain falls. When there is low pressure in the atmosphere then the air bubble that is rising is always hotter than the air around. This heated air will gradually but surely rise. As it rises the heated air will cool down. However it will not cool down as fast as the surrounding air. Thus it will remain hotter than the air around and will continue to rise. Low pressure thus leads to unstable air conditions. If the ground is heated then air will rise. The cool air will produce condensation that will ultimately lead to rainfall.
If the conditions in the atmosphere are at high pressure, atmosphere then the air bubble that is rising is always colder than the air around. The heated air will not continue to rise. As it rises it cools down and thus it will cool down much faster than the air around will. High Pressure causes stable air conditions. If the ground is heated then the air will not rise and therefore the rain cannot condense.
If the conditions in the atmosphere are at high pressure, atmosphere then the air bubble that is rising is always colder than the air around. The heated air will not continue to rise. As it rises it cools down and thus it will cool down much faster than the air around will. High Pressure causes stable air conditions. If the ground is heated then the air will not rise and therefore the rain cannot condense.