Temperatures of 95 degrees in San Juan, Puerto Rico, broke heat records for the island for this week amidst a continuing heat wave.
In addition, the heat index, which measures how the climate feels to the human body by combining the measured temperature with relative humidity, reached 125 degrees Tuesday in Dorado in northern Puerto Rico.
The National Weather Service considers heat indices of 125 degrees or higher to be an extreme danger, with heat stroke likely among those outside in such conditions. The agency puts out heat advisories for any indices above 105 degrees.
The prolonged and lasting heat in Puerto Rico is being caused by a dome of hot air, kept in place by a low-pressure air system near Florida and a high-pressure system just to the east of the island.
As such, the NWS has issued an excessive heat watch that will last until 5 p.m. Saturday. The agency warns that dangerous heat indices of 110 degrees are possible in parts of Puerto Rico on Thursday, Friday and Saturday.
Some experts placed the blame for the prolonged heat on climate change. The jet stream, which helps air systems move, has been weakened by the warming of the Arctic. With less of a disparity between cold Arctic meltwater and oceans at lower latitudes, weather systems have become less mobile.
The Puerto Rican heat wave, ClimaData meteorologist John Morales said, will not break until something shifts in the jet stream to allow the dome to dissipate.
“It’s not just climate, and it’s not just weather. It’s a combination of the two that’s leading to what, frankly, is a dangerous situation,” Mr. Morales told NBC News.
In addition to the slowed-down jet stream, dust blowing across the Atlantic from the Sahara Desert is drying out the air around Puerto Rico.
Hot sand inside nighttime clouds “is acting like a blanket. It’s like clouds that we see sometimes in the evening keeping those temperatures warmer,” Fox Weather meteorologist Stephen Morgan said.
Such temperatures make heat exhaustion probable and heat stroke possible the more time a person spends outside.
Those seeking refuge indoors on Monday were left out of luck when the heat’s strain on the island’s electrical system caused a unit in a power plant in Salinas, Puerto Rico, to fail. Over 40,000 customers were left without power.
The demand on that unit, 3,072 megawatts, was the largest strain placed on the island’s power supply this year. A boiler failure and further strain Tuesday left 100,000 total customers without power that night, with power being mostly restored island-wide by Wednesday.
Temporary and intermittent outages remain a concern, Luma Energy, the owner of the island’s power utility, warned Wednesday.
• Brad Matthews can be reached at bmatthews@washingtontimes.com.