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Source: Washington Post

Aug 9, 2023

Hot tub-like Persian Gulf fuels 158-degree heat index in Iran

By Ian Livingston

Fueled by water temperatures in the upper 90s (upper 30s Celsius), the Persian Gulf region is enduring a brutal combination of heat and humidity that is making it feel intolerable.

In coastal Iran on Tuesday, the heat index leaped as high as 158 degrees (70 Celsius), a level so extreme that it can test the ability of humans to survive outside for more than a few hours.

Heat indexes have regularly surpassed 140 degrees (60 Celsius) in the region in recent weeks, while nights have offered little relief. In populous cities such as Abu Dhabi in the United Arab Emirates and Kuwait City, heat indexes have only fallen to 100 to 120 degrees (37.8 to 48.9 Celsius) after dark.

Excessive heat is very much the norm in this region, but it is now particularly intense as the planet reaches its highest temperatures on record.

In recent days, Persian Gulf sea surface temperatures have risen as high as 97.6 degrees (36.4 Celsius), the highest in 20 years of satellite data at this time of year. The hot tub-like waters are similar to those recently observed near the Florida Keys as oceans worldwide set records for warmth.

Sea surface temperature in the Persian Gulf. (Ian Livingston)

This summer has featured unusually extended spells of scorching weather in the Middle East as zones of high pressure — known as heat domes — have sprawled across a region from North Africa through southern Europe and South Asia.

August opened with a two-day countrywide shutdown in Iran as temperatures soared to at least 126 degrees in the Khuzestan province. The southern Iraq city of Basrah was similarly hot. Temperatures also soared past 124 degrees (51 Celsius) in Ahvaz, Iran, which holds the record for Asia’s highest temperature, 129 degrees (54 Celsius) in 2017.

The baking Persian Gulf has delivered particularly high heat indexes in recent days. On Tuesday, a location on the Iranian island of Qeshm at the intersection of the Persian Gulf and Gulf of Oman reached a heat index of 158 degrees (70 Celsius). In July, this same area saw levels up to 165 degrees (73.9 Celsius).

Maximum hourly heat index on Tuesday. (Ian Livingston)

Farther north along the gulf, the oil and energy hub of Asaluyeh, Iran, saw its heat index reach 146 degrees (63.3 Celsius) Tuesday and 148 degrees (64.4 Celsius) Wednesday. Its August peak was 153 degrees (67.2 Celsius) on the 5th. The average daily low for heat index in the same period was 107 degrees (41.7 Celsius). Through the 9th, the 24-hour average heat index has been a sultry 126 degrees (52.2 Celsius).

The major port city of Bushehr, roughly 150 miles up the coast from Asaluyeh and home to Iran’s controversial nuclear program, has endured unusually extensive periods of extreme heat indexes this year. Data processed by the Iowa Environmental Mesonet shows that excessive heat indexes of 118 to 128 degrees have occurred two to three times more often than normal.

The Persian Gulf waters have promoted suffocating humidity levels. Dew points — a measure of humidity — have persistently reached 90 to 95 degrees (32.2 to 35 Celsius) in adjacent land areas; in the United States, any point over 70 degrees (21.1 Celsius) is considered uncomfortably humid. And peak sea surface temperatures in the region have trended upward in recent years.

Persian Gulf sea surface temperature maximum over the last 20 years.

The combination of the searing heat sourced from nearby deserts and extraordinary humidity from the gulf results in a sweltering setting not seen elsewhere on Earth.

As the planet warms, places in and around the Persian Gulf region are expected to become increasingly inhospitable, and the footprint of unbearable heat will grow.

Ian Livingston is a forecaster/photographer and information lead for the Capital Weather Gang. By day, Ian is a defense and national security researcher at a D.C. think tank. Twitter

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