Warner Valley, CaliforniaWarner Valley is a census-designated place in Plumas County, California. Warner Valley sits at an elevation of. The 2020 United States census reported Warner Valley's population was 8.GeographyAccording to the United States Census Bureau, the CDP covers an area of 17.4 square miles, 99.83% of it land and 0.17% of it water.DemographicsWarner Valley first appeared as a census designated place in the 2010 U.S. census. The 2020 United States Census reported that Warner Valley had a population of 8. The racial makeup of Warner Valley was 7 White and 1 Asian. Hispanic or Latino of any race were 0 persons.EducationThe school district is Plumas Unified School District.