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Drought is a natural phenomenon in which rainfall is lower than average for an extended period of time, resulting in inadequate water supply. Extended dry periods have become more frequent in parts of the United States during the past several decades, especially in the southwestern and eastern United States.

Many factors can influence how a drought will impact a community. Some of these factors include the drought severity in that community, the local water system capacity and infrastructure, economic development, and the community's ability to alleviate drought-related effects. Drought also has public health implications. For example, severe drought can negatively affect air quality because of the increased risk of wildfires and dust storms. This can worsen respiratory illnesses, such as asthma. To learn about more ways that drought can impact health, see Drought and Health.

The Tracking Network includes data on drought duration and severity in the United States. These data can be used to better understand the connection between drought, other environmental conditions, and health effects. To learn more about the data sources for drought, see Tracking Drought.