Maybe. But I was struck by how the map represents a general trend of movement away from the cold upper Midwest and Northeast to the warmer Southeast and Southwest. Kind of makes me doubt the premise of this being driven by taxes.
Errr... what? There are THREE, count them, three big draw states that happen to be in the south (part of the country for those that will be screaming about IT'S THE SOUTHWEST!): Texas, Arizona, and Florida. They also happen to have beneficial tax laws.
Look around the Northeast: everyone is fleeing the high tax states to the low ones: Maine, Vermont, New Hampshire. (Incidentally, those fleeing are moving NORTH from Massachusetts and New York.)
The South (that is growing) all tend to have laws that encourage such growth. The fact that California is one of the BIGGEST losers and has the absolute best climate in the contiguous states and has seen a MASS migration out rather belies your "impression".
People used to go to California for opportunity AND the climate. The climate hasn't changed. Or, perhaps, I should say the weather hasn't changed. The economic climate certainly has.