Storm Lake, IA has a population of 10,768 and is the 3,733rd largest city in the United States. The population density is 2,042 per sq mi which is 3638% higher than the Iowa average and 2154% higher than the national average. The median age in Storm Lake is 28 which is approximately 25% lower than the Iowa average of 38. In Storm Lake, 53% of the population over 15 years of age are married, 48% speak English and 36% speak Spanish. 45% of Storm Lake residents were born in Iowa, 25% were born out of state, 1% were born outside of the United States and 29% were foreign born.