AbstractObjectives: Our goal was to examine the relationship between BMI and climate amenable for physical activity at the county level in the U.S.Research Methods and Procedures: Using Geographic Information Systems tools and 6‐year National Oceanic and Atmospheric Administration station hourly weather records, an index of amenable climate was derived for all U.S. counties. This index was linked to individual BMI in a multi‐level analysis that accounted for other individual characteristics from the 2002 survey of the Behavioral Risk Factor Surveillance System.Results: There was an inverse relationship between climate amenable to physical activity and BMI at the county level after controlling for individual risk factors, county road density, and median household income and unemployment rate. Residents in high climate‐amenity counties tended to have a lower BMI.Discussion: The contribution of less amenable climate to overweight and obesity in the U.S. is likely to be substantial because it cuts across wide geographic areas. Health promotion strategies that promote mixed land use or other urban design conducive to walking and other physical activities should consider broader environmental disamenities to mitigate their influence. Strategies for outdoor physical activity should also be tailored for people of different racial groups and educational backgrounds due to observed differences in their response to climate amenity.