Did you feel a shift in the cosmos yesterday? A slight bending of the time-space continuum? Well, perhaps it wasn't that cataclysmic, but there was a notable change in the gardening world: the USDA released its long-awaited revision of the Plant Hardiness Zone Map. The new map uses 30 years of weather data and does show generally warmer temperatures shifting northward. So, many people will find that their zones are now a notch higher. Here in Alameda, for example, we've moved from Zone 9b, with low temps from 25 to 30F, to Zone 10a, with low temps from 30 to 35F. That sounds about right to me since getting below 30F here is quite rare. If you want to find the new zone for your specific area, click here and plug in your zip code.
So what does this new zoning mean for you? Nothing radically different. It might justify venturing a little more into the world of tropical plants. Maybe you'll want to try growing your own bananas, which require Zone 10-11 temps. But keep in mind that this "new normal" means that we might have fewer chill hours (hours below 45F) in the winter that some plants require for flowering and setting fruit.
But rather than getting too caught up in zones and average temperatures, the best approach is to get to know your own garden. Identify the warmest spots (probably against a south-facing fence or wall) and the spots most vulnerable to frosts. Take notes and plant accordingly. Take more notes. Pretty soon you'll have more accurate data to work with than the USDA will ever be able to provide you. And then you can name or number your zone anything you want.