Prime-age male labor force participation has trended downward since the 1970s. I develop and test a task-based model in which rising temperatures shrink the outdoor-job premium, by shifting firm labor demand and raising the value of time at home, thereby lowering participation. Measuring daily work-hour temperature across US commuting zones using weather-station data spanning five decades, I find that sustained exposure to extreme heat and cold reduces prime-age men’s participation, especially among non-college workers in nonmetropolitan areas, with little effect for women. The decline is stronger where outdoor jobs and housing amenities (e.g., air conditioning) are more prevalent. Climate change deepens regional and educational divides in men’s labor market attachment.

We study the impact of climate change on the labor share. Combining newly constructed US county-industry-level labor shares with climate variables, we find that extreme temperatures reduce the labor share, with stronger effects in industries with higher climate exposure and automation potential. Extreme temperatures also accelerate robot adoption. A back-of-the-envelope calculation suggests that the within-county-industry response to climate change accounts for 15% of the decline in labor share since 2000. Over the 20th century, however, the opposing effects of decreased cold days and increased hot days offset each other, consistent with the historical stability of labor share.