Beyond its environmental damage, climate change is predicted to produce significant economic costs. Combining novel high-frequency geospatial temperature data from satellites with measures of economic activity for the universe of US listed firms, this article examines a potentially important channel through which global warming can lead to economic costs: temperature uncertainty. The results show that temperature uncertainty—by increasing power outages, reducing labor productivity, and increasing the degree of exposure of firms to environmental and non-political risks, as well as economic uncertainty at the firm-level—persistently reduce firms’ investment and sales. This effect varies across firms, with those characterized by tighter financial constraints being disproportionally more affected.