Climate change and urbanization pose new challenges and opportunities to the effort to alleviate poverty in developing countries. This dissertation is comprised of three chapters that examine questions relating to the microeconomics of poverty, nutrition, and development in light of these ongoing trends. The first chapter, joint with Ariel Ortiz-Bobea and John Hoddinott, is motivated by the recent literature showing that extreme heat shocks can lead to poor economic and health outcomes. We construct hourly bins of temperature exposure to estimate the effects of extreme heat on early child nutrition, a health outcome correlated with educational attainment and income in adulthood. Linking 15 rounds of repeated cross-section data from five West African countries to geo-coded weather data, we find that extreme heat increases the prevalence of both chronic and acute malnutrition. We find that a 2 degree Celsuis rise in temperature will increase the prevalence of stunting by 3.9 percentage points, reversing more than half of the progress made on improving nutrition during our study period. In the second chapter, I re-examine the historical urban nutrition advantage in Bangladesh. Despite rapid and widespread rural-to-urban migration, I find that higher levels of wealth and education in urban areas continue to drive the urban nutrition advantage in Bangladesh. Among the youngest children, however, the gap is not significantly different from zero, consistent with the strong breastfeeding practices observed among rural mothers. Yet, by 24 months, rural children from low-income households are worse off compared with the average child, suggesting a need for more research on the determinants of other (non-breastfeeding) intermediate outcomes and nutrition-related behaviors in rural households. The third chapter examines the effects of financial stress on decision-making among the urban poor, a large and growing population in the developing world. I conduct a lab-in-the-field experiment with market vendors in Addis Ababa where I use mystery shoppers to exogenously increase vendors' earnings. I then measure deviations from utility-maximizing choices and uptake of a budget-expanding opportunity. I find that there is no impact of a single-day revenue increase on decision-making among the poorest vendors. However, I find descriptive evidence that economically beneficial decisions are more common among those with lower than expected monthly wages, suggesting that in the medium term, the income channel dominates the cognitive channel.