Wow, you know how to ask hard questions. It is hard to answer because varieties of the same family may bloom early or later. It also depends on the weather. I have seen red buds in full bloom in late February along I-59 between Gadsden and Chattanooga. Last year (2009) I thought we would see dogwoods frosted-out the week before Easter (April 12). If you are looking for spring blooms, I suggest the following TREES: white & red dogwood; flowering crabapple (Brandywine double is a good one); tulip magnolia (pink for early blooms and purple for later blooms), flowering purple leaf plum, ornamental peach (Peppermint), quince tree(not the bush). Contact your local Auburn or Tuskegee cooperative extension agebt in your county. They can help. Use the link, pick state and county.

Here is a link that might be useful: Cooperative Ext Service

I'll add Carolina Silverbell to the list. We really like ours.

Gosh, looking back at this question, I think of the scads of spring flowering trees that do so well in this region! Star Magnolia, and those wonderful 'Little Girl' hybrids! They're so sweet. Red Buckeye is a favorite of mine, so is Fothergilla. And on and on.

Your choices should be determined by your site: the kind of soil, soil pH, drainage, amount of direct sunlight, space (above and below ground), and other factors.

a favorite for me is our native chionanthus virginicus (american fringetree or grancy greybeard). it is usually at peak here in auburn about the middle of april so might be more toward the end of the month in your area. it makes a fine, small specimen tree that flowers over a period of a couple of weeks and smells very nice.
best shape and flowering in a sunny site but can also be found as an understory tree in woodlands.

Here is a link that might be useful: fringetree