http://sickplants.tamu.edu/

I found this link, not sure it's what you need, but google 'chill hours dallas' and a whole bunch of links come up.

If you are talking about Dallas, Georgia, here is a link to chill hours in Georgia. If you are talking about Dallas, Texas - which didn't even occur to me when I first read this post - I couldn't find it.

Here is a link that might be useful: Georgia Chill Hours

Your local County Agent would have this information, I'm sure. It is necessary to know when selecting fruit tree varieties. Texas A & M (TAMU)(Aggies) is probably the host for this data, but I couldn't find a link on their site.
Rb