Monarch Weather

Wx and the City

Monarch butterflies gather around a flower. Courtesy U.S. Fish and Wildlife Service.

I love fall. Not just the crisp weather and full-blazed foliage, but also because it's a season of transition. For example, each fall, millions of monarch butterflies all over Canada and the U.S. migrate south to Mexico and California for the winter, before their offspring migrate back to the north come spring and summer. Monarchs are the only butterflies to make two-way migrations.

'Tis the season for "just right" weather this month: not too hot, not too cold, not too stormy, but just right for monarchs. A combination of cool temperatures, the changing angle of the sun, and many other environmental cues unknown to scientists (possibly even Earth's magnetic field, much like homing pigeons are thought to use) help the butterflies know when and where to start migrating.

Keep reading for more on monarchs. How long will monarch-friendly weather continue? See our full forecast through the holiday weekend, and SkinsCast for Sunday's game at FedEx.

Like migratory birds, monarchs cannot survive cold winters -- they are thought to have originated in the tropics. (Did you know that no butterfly can fly if its body temperature goes below 86 degrees Fahrenheit?)

Migrating monarchs go through a phase called "diapause," in which they stay in a sort of teenager phase over the winter to conserve energy before finally maturing and mating in the spring. While migrating, they cluster together on tree branches to stay warm. (Aww, huddling butterflies...don't we all need someone to cuddle with during cool fall nights?)

Will so many small movements of air from millions of flapping wings affect the mid-Atlantic's weather over the coming weeks? Capital Weather Gang may never know. But, you can read Steve's post to learn more about the "butterfly effect."

Apparently, it can take up to two months for monarchs to fly from Washington, D.C., to their winter nesting grounds in Mexico, depending on temperature and wind conditions. While you're monitoring the air waves for migratory birds this month, keep a look out for tiny black-and-orange flocks that don't look quite like birds -- they might be Monarchs.

Have you seen any Monarchs in the Washington metro region yet? Perhaps huddled together in tree branches during the recent cool nights, or catching a fall breeze over the Beltway? You can monitor the migration yourself and report your sightings here.