Climate change increases risks to the operations and financial reliability of drinking water utilities across the United States. Here we develop a comparative climate risk index that includes hazard, vulnerability, and exposure components for 1455 medium and large municipal US drinking water utilities. We find that 67 million customers are serviced by utilities with higher climate risk. Drinking water utilities in the Western US have higher risk due to expected large changes in climate hazards, while utilities in the Northeast and Midwest have higher risk due to existing vulnerabilities and exposure. We use this climate risk index, along with an analysis of municipal bond official statements, to identify utilities in need of climate adaptation and resilience planning.