Heat updates: 113 million under alerts; record June heat; 'Cerberus' heat wave in Europe

A dangerous, unrelenting heat wave scorched much of the south-central and western U.S. on Thursday, bringing near-record temperatures and an increased risk of wildfires to a large swath of the nation.

As of Thursday afternoon, more than 113 million Americans were under some form of heat alert, the National Weather Service said. The alerts, which include excessive heat warnings and heat advisories, stretched some 2,000 miles from Oregon to Louisiana.

Locations including Phoenix and Las Vegas, which were both under excessive heat warnings, could each challenge all-time record highs over the next few days, AccuWeather said, as temperatures soar above 110 degrees.

“Unfortunately, the long-term outlook through the weekend and into next week is for an increasingly significant and oppressive heat wave,” the weather service said.

Meanwhile, while the U.S. suffers with extreme heat, the planet as a whole just endured its warmest June on record, climate scientists reported Thursday.

Around the world, scientists say the unusually warm temperatures for this time of year, even in the Antarctic where it’s winter time, are yet another example of a changing climate, made worse by fossil fuel emissions.

Heat can be dangerous and deadly

The extreme heat and blazing sunshine can cause people to become rapidly dehydrated, experts warn. People are urged to avoid strenuous activity during the daylight hours, to increase their intake of fluids and seek an air-conditioned environment when possible to avoid the potential of heat exhaustion and heatstroke, AccuWeather cautioned.

“Please plan accordingly, this is not the time to be hiking or be outside for long durations,” the weather service’s Los Angeles office said on Twitter. “If you need to work outside, shift hours to the early morning, take frequent breaks and hydrate!”

Extreme heat is the deadliest weather-related event in the United States. It kills more people than tornadoes or hurricanes – combined.

Federal agencies report about 700 Americans die each year from extreme heat, but some studies estimate that figure could be closer to 1,300 deaths a year. Another study found up to 20,000 deaths may have been linked to extreme heat from 2008 to 2017.

June was globe’s hottest on record, NOAA and NASA say

Our summer of heat records continued Thursday with announcements from both NOAA and NASA that June 2023 was the Earth’s hottest June on record. NOAA’s records go back to 1850, while NASA’s go back to 1880.

June 2023 also marked the 47th-consecutive June and the 532nd-consecutive month with temperatures above the 20th-century average, NOAA reported.

In addition, NOAA said the first half of 2023 ranked as the third-warmest on record, with a global temperature of 1.82 degrees above the 20th-century average. There is now a 97% chance that 2023 will end up as one of the five hottest years on record.

The European Copernicus Climate Change Service and Berkeley Earth also said it was the hottest June on record.

Scientists say the warmth the planet is enduring this year is due to a combination of human-caused climate warming and the strengthening El Niño climate pattern in the Pacific Ocean.

“The onset of El Niño has implications for placing 2023 in the running for warmest year on record when combined with climate-warming background,” University of Georgia meteorology professor Marshall Shepherd said last month.

El Niño expected to persist through the winter

Speaking of El Niño: the famed climate pattern is expected to persist through the upcoming winter of 2023-24, federal forecasters from the Climate Prediction Center announced Thursday. Specifically, there is a greater than 90% chance that El Niño will continue through the winter, the CPC said.

Forecasters also said this El Niño should be of “moderate to strong intensity,” and added there’s a one in five chance that it becomes “historically strong,” rivaling the winters of 1997-98 or 2015-16.

Florida also under heat advisories

Before sunrise Thursday, the heat index on Virginia Key in Miami was 99.3 degrees, the dawn of yet another oppressively hot day in an extended heat wave blanketing South Florida.

As of Thursday, Miami is at an unofficial record of 33 days with a heat index over 100 degrees, breaking a record set in 2020, according to Brian McNoldy, a senior research associate at the Rosenstiel School of Marine, Atmospheric and Earth Science at the University of Miami. The unofficial record comes from the historical records for a weather station that’s been in place on the south side of Miami International Airport since 1948.

Ten counties in Florida are under an advisory for heat index readings above 100 degrees on Thursday, according to the National Weather Service. The heat index – what the air temperature feels like – comes from a combination of air temperature and dew point temperature.

Oceans are hot, hot, hot

Sea surface temperatures in South Florida have been running up to 5 degrees above the 1991-2020 averages, and are the hottest they have been during this time of year since at least 1985, according to NOAA.

The ocean heat wave is among a series of extreme marine heat waves baking more than 40% of the world’s oceans. Global sea surface temperatures were at a record high for the time of the year in May and June, the World Meteorological Organization said this week. And the heat waves are expected to expand to 50% by September.

In the North Atlantic, ocean temperatures are “much higher than anything the models predicted,” said Michael Sparrow, head of WMO’s World Climate Research Department.

The heat in the Atlantic is caused by a combination of short-term circulation in the atmosphere and longer-term changes in the ocean, the Copernicus Climate Change Service has reported.

“It is not believed to be linked to El Niño, which is only just becoming established in the tropical Pacific and is expected to influence temperatures later in the year and into 2024,” the WMO said.

Above normal ocean heat can impact corals, fish, ocean circulation and the weather, the WMO said. Coral reef scientists and marine biologists are greatly concerned about the impact on corals and other sea life.

If the high temperatures linger through the summer, “corals will experience bleaching,” Derek Manzello, coordinator of NOAA’s coral reef watch said this week. A bleached coral is essentially starving to death because it has lost its main source of nutrition — the algae that live symbiotically within its tissues.

“If the heat stress does not subside, the coral will die,” Manzello said. “Corals can recover from bleaching if the heat stress subsides,” he said, but even when they do they may have impaired growth and reproduction and are more susceptible to disease.