Weather question?

Although your question is kind of vague, what I think you don't get is that atmospheric pressure is relative. High pressure is just a comparison to what it's replacing. For example, if you open your refrigerator on a hot day, it's cooler (and more dense) than the surrounding air. If, however, the house was minus 5 degrees, the temp is actually higher in the fridge, and less dense. It's all relative.