July 18, 2023 - Millions face extreme heat in the US, Europe and China

The Persian Gulf International Airport weather station in southern Iran registered a heat index value — the apparent “feels like” temperature to the human body — of 152 degrees Fahrenheit (about 67 degrees Celsius) on Sunday.

The recorded temperature on Sunday around 12:30 p.m. local time was 104 degrees Fahrenheit (40 degrees Celsius).

Heat indexes of 160 degrees Fahrenheit are widely considered the upper threshold of what humans can endure for any more than a few hours. As heat index values climb to these thresholds, the human body feels strain and can lose its ability to cool itself down.

As of 10 a.m. ET Tuesday (5:30 p.m. local time), the recorded heat index was 130 degrees Fahrenheit (47 degrees Celsius). Earlier Tuesday, the heat index reached 146 degrees Fahrenheit (63 degrees Celsius).

This oppressive heat wave is part of the global average temperatures that have remained at record levels since July 3.

According to National Oceanic Atmospheric Association, the “highest dew point ever recorded, 95°F (35°C), was recorded at Dhahran, Saudi Arabia, on July 8, 2003. With an air temperature of 108°F (42°C), the heat index was 178°F (81°C).”

Cyprus’ Department of Meteorology has issued an extreme high temperature warning on Tuesday, marking the seventh consecutive day of such temperatures in the country.

In a tweet, the Department of Meteorology said that temperatures are expected to reach up to 41 degrees Celsius (105.8 degrees Fahrenheit) over Cyprus' inland areas on Tuesday, and 33 degrees Celsius (91.4 degrees Fahrenheit) over the country’s higher mountainous areas.

The extreme high temperature warning is set to stay in place until at least Wednesday evening. The warnings are issued on a day-to-day basis.

Greece continues to battle wildfires on Tuesday near the capital city of Athens and in other parts of the country. 

The wildfire that broke out on Monday southeast of Athens and near popular seaside towns is now under control, according to the Hellenic Fire Service. The situation near the seaside resort of Loutraki in the Peloponnese region, where a second large fire started yesterday, is improved although there is occasional rekindling that firefighting forces are attending.

The majority of the fire service is now focusing on a large fire that broke out late Monday in the area of Dervenochoria, north of Athens, which is still spreading and heading southwest. Two-hundred-and-fifty firefighters with 75 fire engines, 11 aircraft and nine helicopters are trying to control the fire, according to the service.

Greek Prime Minister Kyriakos Mitsotakis is returning to Athens earlier than expected due to the ongoing wildfires raging in Greece, his office said on Tuesday.

Mitsotakis was in Brussels attending a summit for European Union, Latin American and Caribbean leaders. His office said that upon arrival, he would go to Greece's response coordination center.

The large fires have caused major damage since Monday, burning down houses, killing animals and destroying land, prompting authorities to evacuate many areas as a precaution.

No casualties have been reported so far. 

The "extreme heat" currently gripping much of southern Europe and the Mediterranean is forecast to intensify by mid-week, and new records may be established, the UN's World Meteorological Organization (WMO) has warned. Many households across Europe have no air conditioning, even as temperatures surpass 100 degrees Fahrenheit in parts of Italy, Greece and Spain. 

Fewer than 10% of European households have air conditioning (AC), according to a 2018 International Energy Agency (IEA) report — the latest data that is available from the agency. In total, the European Union only accounts for about 6% of global AC units.

In contrast, about 90% of households in the US and Japan are equipped with AC. 

"Air conditioning is highly concentrated in a small number of countries, with two-thirds of all systems in use found in just three countries – China, the United States and Japan," the International Energy Agency said in the 2018 report. 

IEA figures published in 2021 show that the United States accounts for about 20% of global air conditioning units and China accounts for 40% of AC units, while the rest of the world accounts for a combined 29%.

"Europeans have generally been less inclined to install an AC compared with their American counterparts until recently, though this is now changing, with AC ownership in Italy, Spain, Greece and southern France rising rapidly in the last decade," the IEA said in 2018.

While the proliferation of air conditioning in the United States, China and Japan helps those countries stay cool in hot weather, it also increases their energy usage and carbon emissions.

"Using air conditioners and electric fans to stay cool accounts for nearly 20% of the total electricity used in buildings around the world today," the International Energy Agency said in its 2018 report. "And this trend is set to grow as the world’s economic and demographic growth becomes more focused in hotter countries."

As the demand for air conditioning increases, European governments are trying to find ways to keep costs and emissions low. 

The Italian government has implemented maximum cooling levels in summer and minimal heating in winter in all public buildings except hospitals. Meanwhile, France last summer implemented fines for shops that keep their doors open even when air conditioning is on.

IEA figures from 2021 show that global CO2 emissions from air conditioning amounted to 994 metric tons, which are predominantly indirect emissions from electricity generation. 

With an estimated 1.6 billion electric air conditioning units around the world – a number expected to triple by 2050 – cooling technology could release enough greenhouse gas emissions into the atmosphere to cause temperatures to rise by 0.5 degrees Celsius by the end of the century, according to Rocky Mountain Institute.

The IEA noted that investing in more efficient AC units could cut future energy demand in half.

With previous reporting from CNN's Eliza Mackintosh and Ivana Kottasová.

Whether you’re without power, enduring extreme heat or trying to save money, there are ways to feel comfortable without artificial cooling.

The body shouldn’t be too hot for too long, as too much heat can harm your brain and other organs, according to the US National Institutes of Health. Sweating is the body’s natural cooling system, but when that’s not enough, there’s increased risk for developing the heat-related illness hyperthermia — signs of which include heat cramps, heat edema and heat stroke. Heat combined with high humidity exacerbates this risk, since the air’s saturation level makes sweat accumulate on the skin, preventing the body from cooling naturally.

Staying cool can be done by using some basic supplies and knowing how to manipulate your home to control its temperatures. Here's how:

Read more tips here.

As more than 90 million people swelter under heat advisories across the country, temperature-related hospitalizations have been consistent across multiple medical centers in Arizona.

Valleywise Health Medical Center emergency room doctor Frank LoVecchio told CNN he has seen an increase in hospitalizations, with three or four cases per shift of patients who faced death without emergency treatment.

Valleywise Health Medical Center has locations across the Phoenix area. The city once again hit 110 degrees Monday for a record-tying 18th consecutive day.

Patients can experience body temperatures of 107 or higher, resulting in death or permanent brain damage. LoVecchio said it could take as little as five to 10 minutes to cause brain cell death at these high temperatures.

Valleywise Health Medical Center Communications Director Michael Murphy told CNN that in some extreme cases, they are placing patients in body bags packed with ice to help cool them off, adding that their burn center has been "slammed"  with patients experiencing contact burns.  

Ben Hatchett, regional climatologist for the Western Regional Climate Center, said he expects this heat to continue for at least two weeks, according to forecast system models.

The planet’s average temperature has been higher than the previous 2016 record every day since July 3 – driven in part by extreme heat waves in the US, Europe and China.

The previous global average temperature record in data tracked by the National Centers for Environmental Prediction was 16.92 degrees Celsius (62.45 degrees Fahrenheit), set in August 2016. 

On July 3, the average global temperature surpassed that record when it climbed to 17.01 degrees Celsius (62.62 degrees Fahrenheit).

It peaked at 17.23 degrees Celsius (63.01 degrees Fahrenheit) on July 6 – this is the current preliminary record.

In the days since, it has not dipped below 16.94 degrees Celsius (62.49 degrees Fahrenheit). On Monday, it had climbed back up to 17.11 degrees Celsius (62.79 degrees Fahrenheit).

While the NCEP’s data only goes back to 1979, these temperatures are “almost certainly” the warmest temperatures the planet has seen “probably going back at least 100,000 years,” Jennifer Francis, a senior scientist at Woodwell Climate Research Center, previously told CNN.

Global temperatures are in overdrive because of a combination of the arrival of El Niño – a natural climate phenomenon in the Pacific Ocean – and the human-caused climate crisis, which is pushing global temperatures steadily higher.

Hungarian authorities have issued a heat alert that is set to last until Wednesday evening.

Temperatures in Hungary’s capital city Budapest are reaching highs of 31 degrees Celsius (87.8 degrees Fahrenheit), while other areas in Hungary are seeing temperatures of up to 34 degrees Celsius (93.2 degrees Fahrenheit).

Extreme heat occurring in countries across the globe is "dangerous" and a "rapidly growing health risk," the United Nations’ World Meteorological Organization has warned. 

“Heat waves are amongst the deadliest natural hazards, with hundreds of thousands of preventable deaths each year,” John Nairn, the organization's senior extreme heat adviser, said Tuesday in a news conference. 

Nairn emphasized the implications of extreme heat on health, including the fact that repeated high nighttime temperatures are “particularly dangerous” and could lead to “increased cases of heart attacks and death,” because the body is unable to recover from sustained heat throughout the day.

Nairn also talked about the reasons why this extreme weather is happening.

“These are not your normal weather systems of the past,” he said. “They have arrived as a consequence of climate change. ... It will continue and it will continue for some time. You have to reverse it. You have to do climate repair to change it."