Drought is a normal, recurring feature of climate. The characteristics of this hazard, along with its far-reaching impacts, make its effects on society, economy, and environment difficult to identify and quantify. A national drought watch system has been recommended as a necessary component of drought assessment and management. The National Drought Mitigation Center, in collaboration with others, has undertaken a number of drought watch activities for the past few years, using a variety of resources available over the Internet. These resources include tools such as the Standardized Precipitation Index, a new drought index that is more reliable for detecting emerging drought conditions.

Drought is an insidious natural hazard that is a normal part of the climate of virtually all regions. It should not be viewed as merely a physical phenomenon. Rather, drought is the result of an interplay between a natural event and the demand placed on water supply by human-use systems. Drought should be considered relative to some long-term average
condition of balance between precipitation and evapotranspiration.
The three characteristics that differentiate one drought from another are intensity, duration, and spatial extent. Intensity refers to the degree of precipitation shortfall and/or the severity of impacts associated with the departure. Intensity is closely linked to the duration of the event. Droughts normally take two to three months to become established but may
then persist for months or years, although the intensity and spatial character of the event will change from month to month or season to season. Droughts, unlike other natural hazards, can affect large areas and complicate assessment and response efforts.

Because of the slow-onset nature of drought, monitoring and early warning is an essential part of a comprehensive drought management plan. The development of an integrated climate/drought monitoring system in the United States has been recommended for some time. Recently, the development of the Internet and the WWW has provided the technology to improve information sharing on those critical elements of the hydrologic cycle required to monitor drought and water supply. The NDMC has taken advantage of this technology by developing a drought watch section on their website, with links to other agencies and organizations. The WDCC has provided the necessary support and motivation to develop a comprehensive regional drought watch system for the western states. This system can serve as a model for a national system in the United States that could be transferable to other regions. New indices, such as the SPI, have provided an important tool in assessing climate conditions and initiating mitigation and response actions.