More than 10,000 American cities and towns have set record-high temperatures this year, with over 7,000 experiencing extreme heat under massive heat domes in March, according to data from the National Centers for Environmental Information and NOAA's Climate Data Online. Northern cities like Billings, MT, set a record of 111°F, while Rapid City, SD, reached 112°F. ClimateCrisis247 identified cities that see at least one day a year over 100°F, with some topping 100°F on more than 10 days annually on average this century. Phoenix leads with a 21st-century average of 111 such days, followed by Las Vegas with 78.