What is Brood X? When do cicadas come out in 2021?

[IronLionZion]

https://www.washingtonpost.com/dc-md-va/2021/04/01/cicadas-come-out-2021-brood-x/?itid=hp-top-table-main

Sometime this spring, billions of cicadas that have been underground since 2004 will emerge en masse and blanket parts of the Eastern United States with their song and, eventually, their carcasses.

If you’re in the right location, they will be impossible to ignore.

That depends on the weather. This brood has been quietly rummaging around underground for the past 17 years and will not emerge until the soil temperature about a foot below ground reaches 64 degrees. Most will wait for a humid (but not stormy) evening to pop out of the tunnels they’ve been building for weeks.

They don’t all appear at once, but it may seem like it.

Where will the cicadas emerge in 2021?
If you live in the D.C. area, lucky you! You’ll be in the middle of cicada-Palooza, where huge concentrations will emerge simultaneously.

Lots of good images and diagrams at link that don't show up completely when hotlinked here.

Swarms of cicadas sound biblical.