‘Paint It Black’ — Exactly How Hot is the Border Wall Going to Get?

In recent weeks, President Donald Trump and Homeland Security Secretary Kristi Noem made headlines with the announcement, complete with video footage of Noem wielding a paint roller, that the full length of the steel bollard border wall between the U.S. and Mexico will be painted black to increase its temperature and deter illegal border crossings. 

Critics have been quick to point out that Mexico’s government authorities are unlikely to allow their side to be painted black, instead opting to paint murals on it. Does the rest of the country realize how hot that black steel wall is going to get, regardless of how the Southern side is painted? This Globe contributor and Phoenix metro area resident asked, so I decided to experiment.

Armed with a Laser Infrared Thermometer over several days, I measured two black painted steel items in my back yard, (specifically a matte-black tractor Quick Hitch, and a high-gloss black Webster charcoal grill) in windy and hot Arizona conditions.

Measured at varying times throughout the day over several days, with local temperatures ranging from 105 degrees to 118 degrees Fahrenheit, the matte finish averaged 146.3 degrees across ten readings, reaching a maximum of 150 degrees. The more reflective steel surface averaged 153.1 degrees across ten readings, reaching a maximum of 162 degrees.

Source: Matthew Holloway, Original work

According to a 2022 Study published by the National Institutes of Health: ’Temperature Profiles of Sunlight-Exposed Surfaces in a Desert Climate,’ “pavement warms up higher than 140°F during the summer and, depending on the time of day, will remain very warm for several hours. Therefore, under the right circumstances, a person walking barefoot in the driveway or backyard can sustain a second-degree burn on the feet in a matter of seconds. Moreover, people can develop third-degree burns if they fall and/or have a syncopal event and remain on the pavement for several minutes.”

According to educational materials released by the Northwest Community Emergency Medical Services System (NCEMSS) in the Chicago area, human skin can tolerate temperatures of up to 111 degrees without injury. 

At temperatures exceeding 140 degrees, a second-degree burn can occur with as little as 5 seconds of contact; at 150 degrees or higher, this duration drops to two seconds. Third-degree burns can occur in as little as three seconds at 140 degrees or just one second at 150 degrees.

The effects of the border wall’s new paint job could also potentially result in a rather sizable, localized “heat island,” albeit a long, thin one, approximately 458 miles long. According to the EPA, “Daytime temperatures in urban areas are about 1–7°F higher than temperatures in outlying areas and nighttime temperatures are about 2–5°F higher.” A temperature increase resulting from the wall’s new black paint job could potentially be higher.

However, that does seem to be the point. As Secretary Noem explained from a press conference at the border wall near Santa Teresa, New Mexico:

“Remember, that a nation without borders is no nation at all. And we’re so thankful that we have a president who understands that and understands that a secure border is important to our country’s future. Now, if you look at the structure that’s behind me, it’s tall, which makes it very, very difficult to climb, almost impossible. It also goes deep into the ground, which would make it very difficult, if not impossible, to dig under. 

Today, we are also going to be painting it black. That is specifically at the request of the president, who understands that in the hot temperatures down here, when something is painted black, it gets even warmer. It will make it even harder for people so we are going to be painting the entire southern border wall black to make sure that we encourage individuals to not come into our country illegally to not break our federal laws but that they will abide and come to our country the right way so that they can stay and have the opportunity to become United States citizens and pursue the American dream.”

One thing seems certain: penetrating the U.S.-Mexico border wall is about to become far more uncomfortable for anyone who attempts to scale it, especially with expected higher surface temperatures and seasonally higher ambient temperatures.