What does high pressure on a barometer usually determine?

High pressure on a barometer is typically associated with clear and dry weather conditions. When atmospheric pressure is high, it indicates that the air is descending, leading to fewer clouds and less precipitation, which can often result in sunny weather. This is why high pressure is usually linked to stable weather patterns, making it less likely to predict events like rain or snowfall.

The other options center around specific weather outcomes or phenomena, such as rain or snow, which are more commonly associated with low pressure systems. High humidity does not correlate directly with high pressure either, as increased humidity can occur in various weather conditions but is not indicative of high atmospheric pressure. Thus, the high pressure reading on a barometer primarily suggests fair weather and stability in the atmosphere, contrasting with the concepts presented in the other choices.