The "Stay Cool Act" seeks to enhance the nation's ability to respond to and prepare for extreme heat events. It establishes a comprehensive framework, beginning with the maintenance of the National Integrated Heat Health Information System (NIHHIS) and the creation of a national ranking system for extreme heat severity by the National Weather Service. Additionally, the bill mandates studies on the impact of naming heat waves and improving data tracking for heat-related deaths. To protect vulnerable populations, the bill authorizes grants for programs that check on seniors during extreme heat events , prioritizing those who are low-income or racial minorities. It also introduces a payroll credit for eligible 501(c)(3) organizations, such as community centers, libraries, and museums, that operate as cooling centers by extending hours or waiving admission fees during heat emergencies. A significant portion of the legislation focuses on community resilience and cooling infrastructure. The Department of Housing and Urban Development (HUD) is authorized to provide grants for establishing and assisting community resilience centers , which offer safe, air-conditioned environments during extreme heat and heated environments during extreme cold. These grants cover facility improvements, cooling equipment, emergency supplies, and operational costs. Further grants are available for community resilience and cooling centers to purchase or repair HVAC systems and passive cooling solutions , including cool roofs, tree planting, and cool pavements. HUD will also fund outreach and publicity efforts to inform the public about the location and availability of these centers. In the realm of housing, the bill mandates grants for installing air conditioners or heat pumps in public housing units and for ensuring safe residential temperatures in all federally assisted dwellings. HUD is directed to revise regulations to include air conditioning costs in utility allowance schedules and to establish safe residential temperature standards for federally assisted rental units. The bill also amends the IRS Code to treat expenses for cooling devices like box fans and portable AC units as medical care. Finally, the legislation promotes urban development strategies to combat heat. It authorizes grants for the construction of usable public water features such as splash parks and swimming pools, which must be free and accessible to all. Two additional grant programs focus on increasing urban vegetation: one for developing and improving high-quality urban green spaces to lower surface temperatures, and another specifically for tree planting to cool surrounding areas. These urban development grants prioritize community involvement and employment opportunities for local residents.