WATCH: Mayflies swarm in Cleveland

The National Weather Service captured an image of a swarm of mayflies in 2017.

CLEVELAND — It's raining mayflies in Cleveland.

The swarm of insects is so large this year that it's showing up on weather radar. The National Weather Service in Cleveland tweeted an image of the mayfly swarm it was able to detect on radar.

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The mayflies began showing up in the Cleveland area around June 18, when a sighting was reported in Port Clinton, Cleveland.com reported.

Mayflies are referred to by other names, such as shadfly, sandfly and fishfly, News5Cleveland reported.

The good news for Cleveland residents is that the swarm of insects won't last long. The individual mayfly's lifespan is only about 24 hours, Cleveland.com reported. The mayflies are a bit late in arriving this year and should only stick around for the next couple of weeks, according to Cleveland.com.

While the swarms can be alarming to some, the appearance of the insects is actually a sign that local bodies of water are healthy, Cleveland.com reported.