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

Heat index in Persian Gulf on Sunday neared the upper threshold of what humans can endure for any more than a few hours. Cyprus issued an extreme high temperature warning for the seventh consecutive day.

If you're just catching up now, here's what to know about the intense heat scorching different parts of the world:

The United States: Temperature-related hospitalizations have been consistent across multiple medical centers in Arizona. An emergency room doctor with Valleywise Health, which has multiple locations across the Phoenix area, told CNN: "The hospital has not been this busy with overflow since a few peaks in the Covid pandemic." The city once again hit 110 degrees Monday for a record-tying 18th consecutive day.

Greece: The battle with wildfires continues on Tuesday near the capital city of Athens and in other parts of the country. The majority of the fire service is now focusing on a large blaze that broke out late Monday in the area of Dervenochoria, north of Athens, which is still spreading and heading southwest. Large fires around the country have caused major damage since Monday, burning down houses, killing animals and destroying land, prompting authorities to evacuate many areas as a precaution.

Cyprus: The Department of Meteorology 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.

Hungary: 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).

Iran: 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.

Global average temperature has been above previous record since July 3: 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. 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. Extreme heat occurring in countries across the globe is "dangerous" and a "rapidly growing health risk," warned John Nairn of the United Nations’ World Meteorological Organization. “Heat waves are amongst the deadliest natural hazards, with hundreds of thousands of preventable deaths each year.”

What to do in these temperatures: Stay hydrated, keep your curtains closed, take cool showers, sleep in linens and place cold washrags or ice packs on your pulse points — wrists or neck — to cool down more quickly.

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Paris 2024 officials said Tuesday that they are closely monitoring the current heat wave in Europe and what that may mean for next year’s Olympic Games, calling it “an increasingly central topic.”

“It's something we're working on a lot. We started by looking at what Tokyo in particular was doing, as it was more used to measures against extreme heat. We're working on a number of different issues,” Chief Executive Officer of Paris 2024 Etienne Thobois told journalists earlier Tuesday.

Thobois held a press event in Paris alongside Tony Estanguet, the president of Paris 2024. He added that organizers are looking to ensure the comfort of both athletes and spectators alike.

“We remain very, very vigilant,” he added, noting that at the same time, balance needs to be struck when it comes to carbon footprint.

The Olympics are scheduled to take place from July 26 to August 11, 2024.

The now yearly extreme heat records come with health risks as well as negative economic and climate impacts, according to a climate think tank.

Record-breaking high temperatures are being reported across the world this week — the latest in a trend caused by the climate crisis. The first week of July was the hottest week on record, data shows.

"If we want our efforts to mitigate climate change to work, we cannot continue to neglect action on adaptation. One does not succeed without the other," Cecilio said on Tuesday, adding that developed countries need to deliver on their financial pledges for climate adaptation at the COP28 UN climate summit in Dubai later this year.

"Together, we need to prepare for more extreme weather events, while making sure we work towards a world where we minimize global warming and its impacts," Cecilio said. "If we do so, people, economies and ecosystems around the world will become more resilient, both today and in the future."

There are more than 900 fires burning in Canada, according to the Canadian Interagency Forest Fire Centre (CIFFC). More than half of those – 590 – are out of control, CIFFC says.  

Parts of many states in the northeastern US, such as New York, Pennsylvania, and New Jersey, are under some sort of air quality alert, according to the National Weather Service.  

Philadelphia declared Tuesday "a Code Orange Fine Particles Action Day" due to smoke from the numerous Canadian wildfires. That means residents are advised to limit strenuous outdoor activities.

"The air quality may vary throughout the city and throughout the day, with some areas having worse air quality," Philadelphia Public Health said in a tweet. 

The Massachusetts Department of Environmental Protection on Tuesday said it was extending an air quality alert in five western and central counties due to smoke from Canada's fires.  

"Smoke is expected to impact air quality today in Berkshire, Franklin, Hampshire, Hampden, and Worcester counties," a release said. "Air quality is expected to be unhealthy for sensitive groups."   

Canada is already on pace to have its worst wildfire season in recorded history, and the season is little more than half over, CNN previously reported. This year's wildfire season is already the country's worst in at least 40 years. 

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.