The climate of the Challis Resource Area is influenced primarily by maritime air carried eastward on prevailing westerly winds. General climatic characteristics are abundant sunshine, low humidity, and high evaporation. The major precipitation source, particularly for winter storms, is the Northern Pacific Ocean. In the summer, however, most of the thunderstorm activity is caused by moisture-laden air originating from the south, off the Pacific coast of Mexico.
United States Department of the Interior, Bureau of Land Management, "Challis Resource Area Proposed Resource Management Plan and Final Environmental Impact Statement Volume 2 (of 2)" (1998). Resource Management Plans (ID). Paper 2.