Climate change impact on "outdoor days" over the United States

Here, we introduce the concept of “outdoor days” defined as those relatively pleasant days when most people may enjoy outdoor activities such as walking, jogging, and cycling. Although most climate studies primarily focus on changes in climate mean and/or extremes, projecting response of outdoor days to climate change is particularly important given their relevance to quality of life for communities. Here, we project how climate change reshapes seasonality of US outdoor days: relatively large drops in summer, late spring, and early fall; and a significant increase in winter. However, despite of global warming, annual outdoor days are projected to change only slightly, with notable exceptions. Consistent with recent observations, we project relatively large drops in southeast (-23%), south (-19%), and Ohio Valley (-18%), and a significant increase in northwest (14%) towards the end of the century. Our findings have implications for quality of life in different regions, and for nationwide travel and tourism.