I have a May baby and it was great that I skipped being pregnant in the summer months, he was just starting to walk when it was the next summer, super cute 6-8 month range during the holidays., a good chance for an outdoor birthday (we're in the seattle area so it's always hit or miss lol) far from the school cut off age, being able to get out with him when he was a small baby.
The cons-- Summer maternity clothes are cuter and I think I might actually enjoy being pregnant in the summer-- I too get depressed in winter. It was soooo hot when he was born that I had to keep him in front of a fan (no A/C here typically) for a lot of the day as my house was about 50 billion degrees w/o A/C. I was fat and felt terrible about my body and did not want to wear summer clothing. I felt weak and couldn't really BE outside with the baby as much as I'd like to be outside because I didn't want to leave a newborn in the sun too much.
So, I think I'm going to start TTC in December and shoot for a Sept-Oct baby. I think it would be fun for a change and I love fall. I also like the idea of wearing big clothing post partum and snuggling in for fall/winter. Oh, it makes me feel all nice inside. lol. Plus-- My ds being a May baby, my dh birthday is Feb, mine is Aug. I think October would be a nice balance of family birthdays and before the holidays. And I think a libra would also be a good balance for the family. Of course that is no gaurantee though