This legislation, known as the Heat Management Assistance Grant Act of 2025, amends the Robert T. Stafford Disaster Relief and Emergency Assistance Act to specifically address extreme heat events. It authorizes the President, acting through the Federal Emergency Management Agency, to provide various forms of assistance, including grants, equipment, supplies, and personnel , to State and local governments for the mitigation and management of such events. To be eligible for this aid, State and local governments must submit detailed assessments, including potential loss of life and revenue, other available resources, and long-term impacts. The President is also empowered to provide hazard mitigation assistance for areas affected by extreme heat, even if a major disaster has not been declared. Furthermore, the bill mandates that FEMA, in coordination with the National Oceanic and Atmospheric Administration and the Centers for Disease Control and Prevention, develop a clear threshold for what constitutes an "extreme heat event" within 90 days of the Act's enactment.