Southern Illinois and central Missouri are getting a little storm. A storm of monarch butterflies.

That's right: droves of monarch butterflies migrating south for the winter made their way onto the National Weather Service's radar. The butterflies showed up as a blueish area on the Weather Service's maps.

The National Weather Service noticed the blueish areas on the radar a few days ago. The organization posted a note on its Facebook page on Sept. 19 saying it realized the area was caused by monarch butterflies.

The NWS wrote that it realized the blueish area was caused by something that was alive because there were high differential reflectivity values, which meant that the radar was picking up oblate figures, which is the shape of a flying monarch butterfly. There were also low correlation coefficients, meaning that the radar was picking up figures that were changing shape, like the flapping of butterfly wings.

The Weather Service ended its post with a kind message to the migrating butterflies: "NWS St. Louis wishes good luck and a safe journey to these amazing little creatures on their long journey south!"

Earlier this year conservationists reported that the monarch butterfly population was under strain due to a decreasing amount of milkweed. Milkweed is vital to the monarch butterfly population, since the butterflies lay their eggs on the plants. Other factors might include extreme winter weather, drought and habitat loss in the United States and Canada, as well as Mexico, where the butterflies spend winters. The extreme cold conditions are harmful to milkweed plants..

Weather radars picked up other flying insects recently as well. Groups of grasshoppers and mayflies appeared earlier this year. The weather radar technology works by sending out beams of radiation that can tell the speed and shape of whatever object it hits. It seems that the technology is not just good for detecting weather patterns, but also swarms of migratory insects.

Although seeing a wave of monarch butterflies or other bugs on a radar may not be useful to a weatherman (partly cloudy with a chance of insects?), the information could be very useful to conservationists who want to study the movement of these flying insects.

The monarch population will be flying south through the United States this month to reach Mexico, where they will spend the winter. If your home is in the path of the migration, it should make for an amazing sight!