It happens once every seventeen years, and it just so happens that 2013 is the year that millions of Cicadas are about to emerge from the ground when ground temperature reaches 64 degrees.
They are relatively harmless, but do travel in swarms like locusts. Toward the end of May or first week of June is when they are expected to emerge from the ground. They hang out above ground for about six weeks to breed, then they die off. In 2030 we'll get another invasion.
The cicadas make a kind of chirping noise, which when multiplied by thousands or millions sounds like the video below.
photo: DanCentury, Flickr