High pressure is nearly always associated with peaceful weather. But, while high pressure brings nice weather, there can also be a down side to its presence.
Because the general motion of air within a high pressure system is downward, the high can trap pollutants near the surface of the earth. Those who suffer from allergies and other atmospheric irritants can be adversely affected by extended periods of high pressure.
This can happen in the autumn, when high pressure settles in for extended periods of time. So, while high pressure often means nice weather, it may also mean increased troubles for some people.