At mid-January 2014, some of our gardeners had snow peas (planted the previous fall) coming up. So, at mid-January 2015, I convinced my long-suffering gardening partner that it was time to plant cool season crops. Really.
Because he's a good sport, he came out with me and we planted snow peas, sugar snap peas, shelling peas, spinach, broccoli (for his dogs), broccoli rabe, lettuce, chard, kale, and carrots. It's been over a week with two brief snows and NO plants have come up yet. I hope I wasn't wrong about this!
So, there's one day left in January but I looked at the Down to Earth calendar for January, thinking that it's never to late to learn what I should have been doing. They say that January is the coldest month in New Mexico. It certainly felt like that yesterday. Low nighttime temperatures in the low 20s. Check. Daytime highs in the upper 40s. Hah! We've beaten that quite a few times and even reached the low 60s once or twice I think. They don't think it's actually time to put out vegetables or too much of anything else. They do recommend getting your tools cleaned, oiled, and sharpened... What was that expression - gentlemen, start your engines...
More seriously, germinating seeds care more about soil temperature than air temperature. Although they will care about air temperature once they poke their leaves above the ground. If you read your seed packets, many will provide information on the required soil temperature and/or the weeks prior to or post frosts. All of the seeds we planted are what are called cool season crops. They tend to be able to go out around a month before the last frost and/or when the soil temperatures are above 40F. Our soil temperatures have been holding pretty steady all winter at about 50F.
The concern, really, with planting this early is when the leaves are up. These particular vegetables can all stand a bit of frost but it will be necessary for me to keep an eye on any night freezes we have coming up and cover the row for the night if necessary. To me, that's a small price to pay to have early vegetables!