Non-college men have increasingly worked outdoors and left the labor force since the 1970s. I develop and test a task-based model in which heat lowers men’s outdoor productivity and raises the relative value of time at home, drawing them out of work. Using work-hour temperature across US commuting zones in 1980–2019, I find that manufacturing decline pushed men outdoors and that hot days reduce men’s participation through both outdoor and indoor jobs unprotected by air conditioning, with little effect on women. Within commuting zones, more exposed occupations lose both employment and wages, pointing to falling labor demand. Warming explains about 10% of the decline among non-college men, mostly through weak attachment rather than permanent exit. A model-based formula suggests that air conditioning in unprotected indoor workplaces would have avoided about a quarter of the resulting income losses.

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.