This study investigates the prevalence and severity of under-insurance among U.S. households using comprehensive new microdata from BlackKnight McDash that links homeowners insurance and mortgage information from 2013-2023 nationwide for 100 million borrowers. We document widespread under-insurance on the intensive margin, particularly among borrowers in high climate risk states, with low credit scores, and high loan-to-value ratios. We examine the role played by household credit constraints by showing that households respond to quasi-exogenous premium increases by both dropping coverage as well as increasing mortgage debt, showing that mortgage credit is used to finance insurance purchases. These results imply that rising premiums increase risks in the mortgage market in two ways, first by inducing households to drop coverage, and second by increasing household leverage. Lastly, we study the broader impacts of rising premiums under-insurance on household financial resilience and default risk.