The first scientific records of weather, water and climate in the western United States were collected during the Lewis and Clark Expedition of 1803 to 1806 as the Corp of Discovery traversed the vast uncharted region between St. Louis, Missouri and the Pacific Ocean. In addition to general daily weather comments and events, journal writers recorded climatic regimes through detailed descriptions of flora and fauna in what are known today as the Narrative Journals. Lewis and Clark kept a separate Weather Diary that documented systematic daily observations of temperature, wind, weather conditions, and river levels. It would be nearly 60 years before systematic daily observations of weather, water and climate would begin in the region explored by this Expedition. The written observations contained in the Narrative Journals by expedition members as well as Lewis and Clark’s Weather Diary have been collated and organized into one document and an overview will be presented.