By Jordan Brennan
In one of the most relentless summers to date, heatwaves have scorched much of the country, breaking thousands of temperature records since early June of this year. The worst, however, may have been saved for last as the most extreme September heat wave ever hit the Western U.S., setting hundreds of records on its own. According to an analysis done by the Washington Post of data from the National Oceanic and Atmospheric Administration (NOAA), more than 7,000 daily temperature records were broken this summer across the United States.
Daily temperature records represent the highest temperature ever recorded at a particular location on a particular date, and are broken more frequently than monthly records. Breaking all-time records, which represent the hottest temperature recorded at a location in its entire history, is even more rare. But other metrics, such as a location’s summer average temperature over time, can offer a longer-term perspective. In using these records and metrics together, they paint a stark image of a country experiencing hotter days that spur on long, intense droughts and larger forest fires.
Weather stations all across the United States feed data to NOAA’s Daily Temperature Database, and out of those stations, around 7,600 have at least 30 years’ worth of daily temperature data. In order to discover where and when temperature records were broken between June 1st and September 7th, the Washington Post performed an analysis of the data provided by these stations. The end result was an interactive map published by the Washington Post that shows daily, monthly, and all-time temperature records that were set/broken in each state.
The first daily records of note were set in Phoenix, Las Vegas, and Salt Lake City. On June 11, Denver hit 100℉, tying its own personal record for the earliest day the city hit triple digits. Also among the scores of heat extremes in mid-June was Tucumcari, New Mexico, whose weather station recorded an all-time high of 112℉. As the heat wave crept further east, records were set from Texas to Wisconsin, and late June brought scorching temperatures into the Southeast, where daily record highs were broken spanning from New Orleans to Raleigh.
Searing temperatures continued to set records in the West and South throughout mid-to-late July, with Salt Lake City tying its all-time high of 107℉ and Oklahoma City climbing to 110℉ – its highest July temperature on record. Texas also registered record-breaking July temperatures, with Houston hitting 105℉ on the 10th and Austin reaching 110℉ on the same day. The end of July brought with it a prolonged heat wave in Northern California and the Pacific Northwest, setting records for the longest streaks with highs at or above 90 and 95℉ in Portland and Seattle, respectively. In the midst of the Northwestern heat wave, a forest fire started near McKinney Creek Road in Northern California, growing into one of the largest and deadliest fires California has seen this year.
The Plains happily welcomed the beginning of August, only to be greeted with an oppressively hot and humid mass of air that caused Des Moines to experience its warmest low temperatures (82℉) since 1936. Meteorologists reported that “corn sweat” – the moisture crops exhale into the atmosphere – intensified the humidity. August was also brutal for the Northeast, as Boston saw six straight days at or above 95℉ between August 4th and 9th. Massachusetts was also among five other Northeastern states that reported their warmest August on record. According to weather experts, the most recent heat wave that gripped California and other areas in the West for more than a week was the most severe to ever be recorded in September. In fact, so far, nearly 300 weather stations have recorded their hottest September temperatures of all-time.
In a stable climate, temperatures will shift up and down like a seesaw, and areas are equally likely to break high temperature records as low ones. But in a warming world affected by climate change, we see that the seesaw has broken, causing a skew towards higher records. Over the past two decades, summers have recorded far more record highs than record lows and, in the past summer alone, more than three times as many high records were broken than low ones. Given NOAA’s report stating U.S. summers are growing warmer at a rate of 1.23℉ every century, the chance of future summers continuing to rank as some of the warmest ever experienced will likely only increase.