Jet stream patterns change in September as the fall equinox approaches. As solar radiation decreases, the jet stream strenghtens and begins to push southward. Cold fronts will dip progressively into the south as the season advances. Monarch use the north winds that accompany these fronts for a free ride to Mexico. In fact, without north winds the butterflies would not have sufficient fat reserves to make it. The temperature contrasts between the poles and southern latitudes is lessening due to climate change and appears to be weaking the jet stream. Will these changing patterns affect monarch migration?
