I ate my lunch outside today without a coat. The sun was so warm, I almost thought about tilling up the garden and planting lettuce.
Even the USDA says it is warmer. A new version of the Plant Hardiness Zone Map is out and compared to the 1990 version, zone boundaries have shifted in many areas. The new map is generally warmer than the previous map. This is mostly a result of using temperature data from a longer and more recent time period; the new map uses data measured from 1976 to 2005.
Plant hardiness zones represent the average lowest winter temperatures, not the coldest it has ever been or ever will be at a specific location. You also need to consider the differences between rural and urban areas, hilltops, low-lying areas near streams, and other local factors.
The most reliable choice is to plant species hardy for a zone colder than your area in the map.
So no lettuce in January for me. Even if it does feel like spring.