Although this surely constitutes old news, I can't stop thinking about the two week cold snap that we had during December. As you probably remember, starting on 12/3 and lasting through 12/13, the nighttime temperatures were below freezing. A few nights saw temperatures in the low 20's and teens. 11 days in a row of below freezing nighttime temperatures completely wrecked our chances at having decent winter harvests. In a "typical" Seattle winter, cold spells would not last this long. Most "winter hardy" plants can easily recover from a night or two of freezing temperatures. 11 days of cold, dry winds effectively stripped all of the moisture from uncovered plants. Garden beds planted with winter crops like romaine lettuce and broccoli look like civil war battlefields. So much destruction, hardly anything has survived.
The amazing thing is that a simple row cover can make a big difference. Aside from the actual temperature, one of the principal reasons a crop will die in the winter is due to the desiccating effect of the wind.