This paper repositions the indoor–outdoor threshold as a neglected yet vital site of climate governance in urban studies. Examining how infrastructure modulates air, temperature, and comfort, it develops the concept of hybrid urban socio-natures as spatial assemblages formed by climate control technologies that dissolve traditional distinctions between inside and outside. Drawing on political ecology, science and technology studies, and critical urban geography, the paper proposes a typology of three governance modes, reversion, extension and inversion, that reveal how cities selectively reorganise thermal boundaries.
Through comparative analysis of New York, Toronto, Ahmedabad and Medellín, it demonstrates how comfort becomes an infrastructural capacity that is unevenly governed, creating new geographies of thermal privilege and exclusion. The paper contends that modulating the indoor–outdoor boundary is a distinct aspect of urban atmospheric governance, in which comfort and exposure are politically contested. The paper highlights this boundary as a domain of infrastructural and social struggle and opens new avenues for urban climate research, placing questions of comfort and thermal justice at the core of urban studies.