Requiring Every American Defense Installation to Nullify Environmental Stresses for Security Act of 2019 or the READINESS Act of 2019 This bill requires the Department of Defense to ensure the readiness of the Armed Forces through a program of military installation resilience plans. These plans, which may include state-owned National Guard facilities, shall contain the following elements, as appropriate: an assessment of current risks and threats, such as changes in environmental conditions, and future risks and threats—based upon authoritative projections of changing environmental conditions—to the resilience of a major installation considered in a master plan during a 50-year lifespan; a description of vulnerable assets or infrastructure located on the installation as well as critical community infrastructure and resources outside of the installation; and a description of measures to mitigate threats to the resilience of an installation and its mission, associated costs of the measures, and agreements that will aid the resilience of the installation and vulnerable community infrastructure and resources.