To assess extreme weather early warning systems in large cities across the world. Among cities with populations above 1 million reporting to the Carbon Disclosure Project Cities Adaptation Actions database from 2021 to 2023, we included those providing a description of at least one adaptation action for a climate hazard in at least one year. We identified cities reporting early warning systems using the United Nations Early Warnings for All framework, which includes four pillars: risk knowledge, hazard monitoring and forecasting, warning communication and preparedness. We also tracked public health engagement in these systems. We identified 182 cities, of which 71 described full early warning systems across the four pillars. Cities in high- and upper middle-income countries described early warning systems nearly three times more often than those in low- and lower middle-income countries. Multihazard early warning systems  were reported by 35 (49%) cities, and many of these involved institutionalized cross-sectoral coordination and funded at least one activity from their own resources. Health was reported as a goal of early warning systems by 58 (82%) cities, although just 29 (41%) indicated a specific role for public health agencies. These findings suggest that many large cities are not covered by these health-protective systems. We recommend development of a city-specific framework for early warning systems that identifies roles for health, and scaling up of these tools, particularly in cities in low- and lower middle-income countries, to ensure strengthened adaptive urban resilience against climate threats.