There’s no migrant "surge" at the U.S. southern border. Here’s the data.

But as you can see, the CBP’s numbers reveal that undocumented immigration is seasonal, shifting upward this time of year. During fiscal year 2019, under the Trump administration, total apprehensions increased 31 percent during the same period, a bigger jump than we’re seeing now. We’re comparing fiscal year 2021 to 2019 because the pandemic changed the pattern in 2020. In 2018, the increase is about 25 percent from February to March — somewhat smaller but still pronounced.

But was 2019 an aberration? In the figure below, we combine data from fiscal year 2012 to fiscal year 2020 to show the cumulative total number of apprehensions for each month over these eight years. As you can see, migrants start coming when winter ends and the weather gets a bit warmer. We see a regular increase not just from January to February, but from February to March, March to April, and April to May — and then a sharp drop-off, as migrants stop coming in the hotter summer months when the desert is deadly. That means we should expect decreases from May to June and June to July.

What we’re seeing, in other words, isn’t a surge or crisis, but a predictable seasonal shift. When the numbers drop again in June and July, policymakers may be tempted to claim that their deterrence policies succeeded. But that will just be the usual seasonal drop.