Question

What kind of weather is associated with a high pressure area and why?

Answer 1

Hint: A pressure system is a relative peak or lull in the sea level pressure distribution. The surface pressure at sea level varies minimally, with the lowest value measured $87$ kilopascals ( $108.57$ in Hg) and the highest recorded $108.57$ kilopascals ( $32.06$ in Hg).

Complete answer:
Low-pressure systems are associated with clouds and precipitation that minimize temperature changes throughout the day, whereas high-pressure systems normally associate dry weather and mostly clear skies with larger diurnal temperature changes due to greater radiation at night and greater sunshine during the day.
High pressure generally means clear skies and drier conditions. In contrast, low pressure generally means some sort of precipitation.
Air sinks towards the surface of the planet in areas of high pressure and the opposite is true for low pressure areas. Because air rises in low pressure areas, it also cools and condenses. This condensation can cause precipitation. Most weather maps show areas where the atmospheric pressure is relatively high, and areas where the atmospheric pressure is relatively low. The isobars around such areas are closed curves with the approximate shape of circles. High-pressure areas are places where the atmosphere is relatively thick. Winds blow outward from these areas, although in a spiraling way. As air leaves the high-pressure area, the remaining air sinks slowly downward to take its place. That makes clouds and precipitation scarce, because clouds depend on rising air for condensation. High-pressure areas usually are areas of fair, settled weather. Low-pressure areas are places where the atmosphere is relatively thin. Winds blow inward toward these areas. This causes air to rise, producing clouds and condensation. Low-pressure areas tend to be well-organized storms.
As moisture-laden warm air rises, it begins to cool. Eventually, it reaches the point where the temperature of the air is low enough to become saturated with moisture. As long as there is dust available for the water to collect on, that moisture starts to condense to form clouds. Cool air sinking toward the ground, by contrast, is growing warmer as it becomes compressed, so cloud formation is inhibited.
That's why high pressure weather systems tend to be free of clouds. Without clouds, there is no rain and hence the weather tends to be clear and fair.

Note:
High-pressure systems are often relatively dry or low in humidity; since the air grows warmer as it sinks and becomes compressed, the amount of moisture it can hold increases, causing more evaporation of water at the surface and hence low humidity.