Non-college men have increasingly worked outdoors and left the labor force since the 1970s. I develop a task-assignment model in which rising temperature lowers men’s outdoor productivity and raises the relative value of time at home, drawing them out of work. Using temperature during working hours across US commuting zones in 1980–2019, I find that manufacturing decline pushed men out of indoor plant jobs into outdoor work and that additional hot days reduce men’s participation through workplaces unprotected by air conditioning. The effect on women is much smaller. Within commuting zones, more exposed occupations lose both employment and wages, pointing to falling labor demand. Since 2000, warming and manufacturing decline each explain about 15% of the participation decline among prime-age men; warming works mostly through weak attachment (e.g., in-and-out) rather than permanent exit.

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.