I ran across a great article on space.com about our new season at http://www.space.com/14951-spring-equinox-early-arrival-2012.html. From the article:
Across much of the United States, this has been an unusually mild winter, especially for those living east of the Mississippi. Not a few people have noted that spring seems to have come early this year. Of course, in a meteorological sense that could be true, but in 2012 it will also be true in an astronomical sense as well, because this year spring will make its earliest arrival since the late 19th century: 1896, to be exact.
Remember, the equinox is defined as the time when the sun’s path in the sky intersects the Earth’s equator, so this is a well-defined time. The equilux is defined as the day when you get exactly 12 hours each of day and night, and this date changes depends on where you are in the world. As for the weather deciding to go ahead and actually act like Spring, that is something else entirely…