For the last 24 hours, we’ve been showing you strange weather radar returns that have been picking up something flying around the Denver metro area.

No, not UFOs. Or even moths. Or migrating birds, which typically make these patterns.

Instead, the National Weather Service says it’s all those butterflies that have been passing through our area in recent weeks.

The radar from Wednesday indicated that those butterflies have been staying close to the ground.

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The Painted Lady butterfly migration across Colorado, on their way to Mexico.

Many people saw those butterflies doing just that.

Weather experts say it takes a lot of butterflies to show up on the radar – and if you went outside, you probably saw … well … a lot of butterflies.

“It’s a special because we have been doing what we need to do as a community,” Mary Ann Colley with the Butterfly Pavilion said. “We’ve been planting the right types of plants, and with the fantastic weather we’ve been having, it’s the right combination of success for these butterflies.”

Weather experts say it’s rare to see enough butterflies to gather together in one site to be able to produce this image.

What you're seeing is actually a unique, natural phenomenon: the annual migration of the Painted Lady butterfly! The species migrates more than 9,000 miles from California to Mexico each year.

The size of the migrations is dependent on spring rains.

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