I was at the garden center today, and there were lots of tomato plants and other summer vegetable plants. I can understand the peas, but squash and tomatoes???

You probably know it better. But I can imagine that in zone 9b/10a,... you can plant tomatoes in certain micro climates right now.

Along the coast, sometimes it's warmer in January than in June. Might be worth a try, particularly under a poly tunnel or some other protection.

I wouldn't go overboard, though. Might start with a cherry tomato plant as a trial.

I agree with the previous poster cherry tomatoes work better in the winter months then bigger tomatoes. Cherries have a wider range of temperatures they will set fruit in.

I suspect that the box stores see a potential for profit and act on it. They wouldn't do it if there would not be some incentive.