Average length of U.S. annual heat wave season
Number of days between the first and last heat wave of the year, based on data from 1961 to 2019 for 50 large metro areas
Heat wave season in the U.S. has jumped dramatically since the 1960s. In the 60s, it was 22 days. By the 90s it had reached 45 days. In the last full decade ending 2019, it had stretched to 69 days
