Humidity levels refer to the amount of water vapor present in the air. They are usually expressed as a percentage, indicating how much moisture the air contains compared to the maximum it can hold at a given temperature. High humidity levels can make the air feel warmer and can lead to discomfort, while low humidity levels can cause dryness in the skin and respiratory system. Humidity is an important factor in weather patterns and can influence climate. For example, areas with consistently high humidity, such as tropical regions, often experience lush vegetation, while arid regions, like deserts, have low humidity and sparse plant life. Understanding humidity levels helps in predicting weather and planning activities.