What term defines the long-term average of weather conditions over 20-30 years?

The term that defines the long-term average of weather conditions over 20-30 years is climate. Climate represents the typical weather patterns experienced in a particular area over an extended period. It includes averages of temperature, precipitation, humidity, wind patterns, and other atmospheric conditions, which helps to characterize a region's overall environment.

Understanding the concept of climate is crucial in distinguishing it from weather, which refers to the short-term atmospheric conditions in a specific place at a specific time. The atmosphere, while related, refers to the layers of gases surrounding the Earth and does not specifically define weather patterns or averages over time. A microclimate describes localized atmospheric conditions that can differ from the surrounding area, usually due to varying factors like topography and human activities, rather than encompassing broader long-term averages. Therefore, climate is the correct term that encapsulates the idea of long-term weather averages.