The record-setting heatwave that has scorched Texas and northern Mexico for the past two weeks is forecast to expand across the south before cooling off by the 4th of July. The abnormal heat would be unlikely without the contribution of climate change.
On 27 June, much of Texas and Louisiana and parts of other southern states were under heat advisories, to the US National Weather Service; abnormally high temperatures in northern Mexico as well. That extends what has been more than two weeks of dangerously hot and humid weather affecting tens of millions of people and straining power grids across the region.
The National Weather Service shows temperatures above 100°F (37°C) heat will continue in the region and spread across much of the south until the end of the month. Things will have mostly cooled off by 3 July except for south Texas and northern Mexico.
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That part of the US-Mexico border has been particularly hot, setting a number of local temperature records over the past weeks in terms of both maximum temperature and the number of hours with excessive heat and humidity.
The border city of Del Rio, Texas, record-highs in a row, reaching 110°F (43.3°C) on 25 June, 4°F higher than the previous record set in 1994. Further south, Laredo, Texas, set at least , including one day the reached 115°F (46.1°C).
“The fact that it’s this hot this early makes me want to weep,” says at Texas A&M University, adding that temperatures in Texas usually don’t peak until August.
The combination of high temperatures and high humidity makes the heatwave more dangerous than high temperatures alone, the National Weather Service has , with reports of some that may be linked to the heat. “It is essential to have a way to cool down and interrupt your heat exposure,” says the agency.
“At these temperatures you’re basically a prisoner of air conditioning,” says Dessler.
The need for air conditioning has driven record demand for energy, bringing power grids unsettlingly close to maximum capacity. In northern Texas and Oklahoma, this strain comes on top of grids from damage caused by severe thunderstorms.
The Texas power grid has set several times during the heatwave and was just a few megawatts shy of an all-time record demand on the evening of 26 June; the organisation that manages Texas’ grid for people to cut back energy use. In Mexico, energy 94 per cent of the country’s total capacity, with local outages reported around the country.
“When we get to an event like this we’re always on the edge,” says Dessler. He says losing power and access to air conditioning during such intense heat is a “worst-case scenario”.
Dessler says the heat is driven by a high-pressure system over the area that formed due to a wobble in the jet stream. That “heat dome” creates stable conditions without wind or rain that enable the sun to heat the air and dry the ground. Those factors are also overlaid on base temperatures that are already warmer due to high sea surface temperatures in the Gulf of Mexico and to climate change, he says.
An by the research organisation Climate Central found that climate change made the high temperatures across the region at least five times more likely. “You’re looking at an event that’s really hard to imagine in a world without global warming,” says at Climate Central.
