A heat wave, a heat dome, desert dust, El Niño, and a "wavy jet stream" all converged in Puerto Rico in June to create scorching conditions and a heat index of 125 degrees in places.
And yet, one expert warned, this likely won't be the only case of "life-threatening" heat this year.
What happened?
As Inside Climate News reported, Puerto Rico's temperatures started skyrocketing on June 5.
That's when Jeff Berardelli (@weatherprof), WFLA-TV chief meteorologist and climate specialist, launched a set of tweets to explain the emergency.
Life-threatening heat today in Puerto Rico so hot that some meteorologists are astonished. And more of the same to come this week. Heat index numbers as high as 115-125 today!! So what is going on? There are many factors, so let's dig in... thread 1/ pic.twitter.com/EMEgVkK9yE
— Jeff Berardelli (@WeatherProf) June 6, 2023
On a heat map, the island resembled a glowing ember, with heat indexes from 90 to 123 degrees Fahrenheit. Heat index is the temperature our bodies feel when humidity makes it harder to cool off.
Berardelli said Puerto Rico was "so hot that some meteorologists are astonished," while providing some potential answers as to how the staggering temperatures occurred.
He first showed how Saharan dust particles had settled over the island, keeping clouds away. Then came a heat dome of high pressure, trapping hot ocean air.
Climate change had warmed the ocean, per Berardelli, and likely affected a "wavy jet stream" that changed normal wind currents.
Then there was El Niño, a natural phenomenon that just recently returned. Its effects are complex, but it's generally the "warm phase" of a months- to years-long cycle that can increase temperatures.
"As we go deeper into 2023, and El Niño intensifies, we should expect a stunning year of global extremes which boggle the meteorological mind," Berardelli concluded. "The base climate has heated due to greenhouse warming, and a strong El Niño will push us to limits we have yet to observe."
Why is Puerto Rico's heat concerning?
Inside Climate News summarized Berardelli's punch line: "Puerto Rico's heat wave shouldn't be viewed as an isolated incident, and … other parts of the world should anticipate similar hot spells in the coming months."
Other experts warn similarly. In May, the World Meteorological Organization reported that "global temperatures are likely to surge" in the next five years due to climate change and El Niño.
When heat indexes reach levels they did in Puerto Rico, it's considered a serious health hazard. On some charts, an index of 125 degrees puts the effect on the human body in the National Weather Service's highest danger classification, where "heat stroke is highly likely."
What can I do about heat waves?
We can all take care of ourselves when temperatures rise. Tips for avoiding heat's dangers include drinking water, limiting exertion, and cooling your heels (and feet).
We can take better care of our planet, too. Any steps to reduce heat-trapping gases — such as switching to a bike, electric vehicle, or public transit, or reducing a home's energy consumption — are steps toward limiting climate disruptions.
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