In the aftermath of an extreme local flash flood in Fort Collins, Colorado in July 1997, the Colorado Climate Center began a small local effort in northern Colorado to engage citizens of all ages in measuring and reporting precipitation. Using a Web-based data entry system, volunteers could enter their observations of rainfall, hail and snow and immediately see the results on maps for their area (www.cocorahs.org). This immediate geospatial feedback has proven invaluable in involving, engaging and maintaining participation in what is otherwise a very low-tech, low-cost informal observing network.

In the years since 1998, the network has grown from a local effort in Colorado to what is quickly becoming a national volunteer network that can broadly supplement and enhance existing manual and automatic observing networks. Furthermore, as the number and quality of precipitation reports increase (currently several thousand observations per day) and the geographic extent broadens, hydrological applications are expanding. CoCoRaHS is now becoming a significant data resource for drought monitoring and drought education. Examples will be shown of precipitation patterns observed with this high definition volunteer network. Also, recent progress on drought monitoring and education will be described along with plans for expanding CoCoRaHS nationally in the next two years.