With the increases in hot weather frequency and intensity induced by observed and predicted climate change, heat exposure is an evolving challenge. We estimated a fixed effect econometric model to data on 5,404 individuals drawn from the China Health and Retirement Longitudinal Study database. These observations were used to examine the effect of heat stress on cognitive performance for those above 40 years of age who are often household decision-makers. We found today's heat stress decreases performance on verbal and math test scores, and that cumulative heat exposure over the last 3 days adversely affects verbal test scores. We also found that middle-aged women and people in rural areas exhibit substantial heat stress-induced reductions on cognitive test scores. This finding implies that continuing climate change may well diminish decision-making capacity and effectiveness.