Illegal border crossings surged in July despite the sweltering heat, defying a historical pattern which holds that migrant apprehensions typically decrease in the summer.

Border patrol arrested over 130,000 individuals seeking illegal entry into the U.S. in July, compared to 99,545 in June, according to preliminary U.S. Customs and Border Protection data obtained by the Washington Post.

The uptick in migrant apprehensions was most noticeable in southern Arizona, temperatures reaching above 110 degrees in the region for much of the last month. In the Tucson sector alone, border patrol agents arrested around 40,000 illegal immigrants, the highest one-month total for the area in 15 years, CBP data indicate.

During the hottest summer months, border crossings have historically dropped. This July, however, the opposite happened, suggesting that other factors were at play.

Prior to the spike in July, there was a massive drop in illegal immigration in June. That was a “temporary wait-and-see respite because of the new supposedly tough asylum rules” that the Biden administration imposed after the expiration of Title 42, the Trump-era Covid policy, Mark Krikorian, executive director for the Center for Immigration Studies, told National Review. During the pandemic, Title 42 authorized border agents to expel migrants as a means to prevent the spread of communicable diseases.

The new Biden rule was touted as a tough carrot-and-stick policy, Krikorian said, allowing border personnel to deny asylum claims made by migrants who had not first applied online or applied for asylum in a country they passed through on their way to the U.S. But illegal immigrants learned they could seek entry via the CBP One app, expanded by the Department of Homeland Security in January. The app lets illegal immigrants make appointments at a port of entry to file asylum claims.

Former acting DHS secretary Chad Wolf recently accused the Biden administration of using the app to coverup the magnitude of recent illegal immigration. He said at a dereliction of duty” hearing targeting current DHS secretary Alejandro Mayorkas that the app could exacerbate the serious fraud that already exists in the asylum process.

“Smugglers figured out they weren’t all that tough,” Krikorian said of what happened in practice after the Biden asylum rules were announced, “so now traffic is back up again.”

California U.S. District Judge Jon Tigar suspended the Biden administration’s new post-Title 42 asylum policy last week, giving the administration two weeks to appeal before the suspension takes effect.

The June decrease and July increase were “completely predictable” because the asylum policy was “so full of loopholes,” Krikorian said. Smugglers then believed it was safe to resume their operations. June was also preceded by an “artificially high” increase in May, when migrants were rushing to get in before Title 42 ended.

Why illegal immigration would not only skyrocket in July but move through Arizona rather than Texas is the more interesting question, Krikorian said.

“Why are numbers going going up in Arizona instead of Texas?,” he said. “That is due at least in part to the fact that Abbott is doing everything in his power to disrupt illegal immigration in the Rio Grande.”

Texas governor Greg Abbott’s administration has been cracking down on illegal immigration by cutting down vegetation often used for cover, expanding the state police presence, and erecting razor wire along the Rio Grande river bank. It’s also positioned brown buoys typically used for maritime harbor security on the water. When someone tries to grab it, it slides back down, preventing them from using it as a flotation device to cross the river.

Last week, the Justice Department sued Texas over the floating barriers, asking the court to order the state to remove the 1,000-foot stretch of buoys installed near Eagle Pass, Texas. It is also sought an injunction to bar Texas from installing new ones.

The state has implemented these measures “in one of the craziest crossing areas on the river to break up the flow,” Krikorian said. “All the things Texas has been doing to try to do the job that the border patrol is not allowed to do is pretty clearly having an effect.”

Likely because of the physical obstacles in Texas, smugglers are taking their business to Arizona, Krikorian said. That’s not reducing illegal immigration, but it is diverting migrants away from Texas.

While 40,000 migrants were apprehended in the Tucson sector of the Arizona quarter in July, the heat in the Yuma sector is even more oppressive, sometimes hitting 120 degrees, which may explain the preference.

Despite the July influx, Erin Waters, a spokesperson for CBP, told the Post that illegal crossings are still lower than the astronomical levels documented in the months before Title 42 ended.

"Unlawful border crossings have gone down since our border enforcement plan went into effect and remain well below the levels seen while Title 42 was in effect," Waters said. "We remain vigilant and expect to see fluctuations, knowing that smugglers continue to use disinformation to prey on vulnerable individuals."

However, it’s unwise to compare illegal immigration numbers from the during and after the Title 42 era, Krikorian said.

“They’re just trying to put a lipstick on a pig,” he said. Under Title 42, border recidivism, or the situation in which migrants who were expelled came back to try again, was really high.

“This is not an encouraging sign,” Krikorian said of the CBP’s words of optimism. “The border crisis is chugging along with the occasional fluctuations but the basic calculus hasn’t changed. If you can get across, the odds are really good that you’ll be let go.”