Improved Soil Moisture and Precipitation Monitoring Act of 2018 This bill directs the Department of Agriculture (USDA) to implement a strategy for improving the accuracy of the U.S. Drought Monitor by increasing the geographic resolution of rural in-situ soil moisture profile observation or other soil moisture profile measuring devices. USDA must prioritize adding in-situ soil moisture profile monitoring stations in states that have experienced D3 (extreme drought) or D4 (exceptional drought) within any six month period from 2016 to the present. USDA shall develop standards for: the integration of data that is derived from citizen science (open collaborations through which individuals or organizations participate voluntarily in the scientific process) into the Drought Monitor models, including data from the Cooperative Observer Program of the National Weather Service; and the collection of soil moisture data that is based on readily available equipment. USDA shall direct the Farm Service Agency and the Risk Management Agency of USDA to use the Drought Monitor in the profile monitoring stations added by this bill, data from the Cooperative Observer Program, and any other applicable data in establishing loss assistance and grazing rates.