If you look at www.hummingbirds.net, you can see a great map showing the northward migration of the hummers, which is updated nearly every day from sightings. I check it every year and have found it to be pretty accurate.
As of this morning, the only sighting posted is on the southern end of the Mississippi / Alabama border, which was posted yesterday.
There is more information that you will ever need about hummers on that website. I did put out my feeder a couple of days ago, ready for the advance scouts to arrive.