This reading, if verified, fell just short of the hottest temperature ever measured on Earth in modern times of 129.2 degrees (54.0 Celsius).
Christopher Burt, a weather historian for Weather Underground, has exhaustively analyzed world temperature extremes and determined the 129.2 degree readings posted in Mitribah, Kuwait on July 21, 2016, and Death Valley, Calif., on June 30, 2013, are the hottest credible temperature measurements that exist in modern records.
Officially, Death Valley set the record for the hottest temperature ever recorded on Earth on July 10, 1913, soaring to 134 degrees (57 Celsius). But Burt posted a devastating critique of that measurement in October 2016, concluding it was “essentially not possible from a meteorological perspective,” and that the weather observer committed errors.
For the 128.7 degree-reading Ahvaz posted on Weather Underground to stand and rank among the highest observed world temperatures, it will require review by the World Meteorological Organization.
The scorching temperature reading was brought about by a dome of heat centered over the Middle East.
The excessively hot air over Ahvaz, a city of 1.1 million people, felt even more stifling due to high humidity. As the temperature climbed into the high 120s, the dew point, a measure of humidity, peaked in the low 70s; a high level for the desert location (due to moist air flow from the Persian Gulf, to the south). The heat index — a measure of how hot it feels factoring in the humidity — exceeded 140 degrees. This combination of heat and humidity was so extreme that it was beyond levels the heat index was designed to compute.
In the Persian Gulf city of Jask, Iran, about 800 miles southeast of Ahvaz, the humidity was even more suffocating. The dew point on Wednesday morning hit 91.4 degrees. Dew points above 90 are quite rare. The highest dew point ever measured on Earth is 95 degrees (35 Celsius), set at Dhahran, Saudi Arabia, on July 8, 2003.
Thursday marked the second straight day of record heat in Ahvaz. On Wednesday, it hit 127.2 degrees (52.9 Celsius), breaking the record for Iran’s hottest June temperature, only to be exceeded the next day.
These Iranian temperature extremes come just a month after several locations in the Middle East recorded their hottest May temperatures during another exceptional heat wave.
On May 28, the western Pakistani town of Turbat hit 128.3 degrees (53.5 Celsius), tying the all-time highest temperature in that country and the world record temperature for May, according to Weather Underground meteorologist Jeff Masters.
At the same time Masters reported that at the military base of Konarak in eastern Iran, the temperature reached 127 degrees, “destroying the record of the highest temperature ever recorded in May in Iran (50.5°C in Bostan in May 1999).”
All of these record-breaking temperatures in recent years, including Thursday’s reading in Ahvaz as well as those set in Kuwait and Death Valley in 2016 and 2013, represent temperature extremes consistent with what climate scientists expect to see in a warming world.
The National Academy of Sciences published a report in 2016 that said worsening heat waves are among the weather events that can be most easily connected to human-caused climate change.
A study published in the journal Nature Climate Change in 2015 cautioned that by the end of the century, due to climate change, temperatures in the Middle East may become too hot for human survival.
Correction, July 3, 2017: The original version of this post said Ahvaz may have tied the world-record high temperature of 129.2 degrees based on an observation posted on the Weather Underground website. It turns out Weather Underground rounds temperatures in Celsius up to the nearest degree, which artificially increased the actual high of 53.7 Celsius (128.7 Fahrenheit) to 54 degrees (129.2 Fahrenheit). This post has been corrected to note that real high was 128.7 degrees (53.7 Celsius) – which is 0.5 degrees lower than the highest observed world temperature in modern times of 129.2 degrees.