Yuma is a city in and the county seat of Yuma County, Arizona, United States. The city's population was 95,548 at the 2020 census, up fro…Yuma is a city in and the county seat of Yuma County, Arizona, United States. The city's population was 95,548 at the 2020 census, up from the 2010 census population of 93,064. Yuma is the principal city of the Yuma, Arizona, Metropolitan Statistical Area, which consists of Yuma County. According to the United States Census Bureau, the 2020 estimated population of the Yuma MSA is 203,247. According to Guinness World Records, Yuma is the "Sunniest City on Earth," promising "sunshine and warm weather at least 91% of the year." Anywhere from 70,000 to over 85,000 out-of-state visitors make Yuma their winter residence.