Recently, the mercury in Death Valley, Calif. climbed to a blistering 128℉ ーthe hottest temperature recorded on earth since 2017. Shortly after, NASA and NOAA announced that global temperatures from the first half of 2020 are the 2nd-hottest on record, just behind 2016. Greenhouse gas emissions are changing the chemistry of the atmosphere, causing our climate to warm to a level that modern society has never experienced.
Extreme heat looks much different today than just fifty years ago. We analyzed how the number of extremely hot days has changed since 1970. While “extreme heat” means something different to each city ー from 70°F+ in Anchorage, AK to 110°F and over in Yuma, Ariz. ー these levels of heat are exceeded more and more often across the United States.
Of the 242 cities analyzed, 142 (59%) experience three or more additional days of extreme heat. The ten cities recording the greatest increases in the number of extremely hot days were all in the southern United States ー seven of which were recorded in Texas alone. All of the top ten recorded more than three additional weeks of extreme heat since 1970, while Miami led with a startling increase of seventy-seven days!
Extreme heat is dangerous. It’s the top weather killer (surpassing flooding and tornadoes), and is especially difficult to shelter from this year, as a result of the pandemic. The heat poses a serious occupational hazard for outdoor workers and disproportionately threatens lower-income communities, whose access to air conditioning is typically more limited. In recent years, many cities have stepped up their adaptation efforts, coming up with novel strategies and protocols for protecting citizens during bouts of extreme heat. Ultimately, though, there’s no way around cutting our greenhouse gas emissions if we hope to turn down the global thermostat.
Last week, NOAA released a report finding sea level rise flooding of U.S. coastlines is happening now, and is becoming more frequent each year. Check out Climate Central’s Coastal Risk Screening Tool to explore flood threats along the U.S. coasts.
Data was gathered via the Applied Climate Information System. To select the primary temperature threshold for each city, an “extremely hot day” is defined as the highest 5°F increment temperature that occurred at least four days during more than half of the years of the study period (1970-2019). Change in the number of days is based on linear regression.
Climate Central’s local analyses include 244 stations. However, for data summaries based on linear trends, only 242 stations are included due to large data gaps in St. Johnsbury, Vermont and Wheeling, West Virginia.
NOTE: If you would like a different temperature threshold for your city, please let us know.