For much of recent history, undocumented immigrant traffic across the U.S. southern border has followed a surprisingly stable pattern. Year after year, crossings spike in the spring and drop slowly throughout the summer before getting a bump again in August:

In 2014, however, this pattern collapsed. Since then, the only consistency in southern border migration has been the lack thereof:

For perspective, here's all that data together:

There are likely a number of factors that led to this pattern's disruption. The most obvious, however, is the decreasing number of Mexican seasonal laborers coupled with increase of Central American asylum seekers. These two factors appear to bisect in 2014:

The San Antonio Express-News has written at length about the impact of these trends and the forces behind them, including Jason Buch's 2016 feature on San Salvador gang violence and its role in Central American northward migration:

And, in turn, the resulting surge in undocumented families crossing the border and claiming asylum:

Despite these trends, northbound crossings at the U.S./Mexico border have been on a steady decline for over a decade:

Locally, however, apprehensions are now higher in the Rio Grande Valley than anywhere else along the border:

Today, the vast majority of undocumented immigrants, from Mexico or elsewhere, are entering the country right below San Antonio.