Last night was unbearable! My mom didn't want to hear about it, considering she was experiencing -8 degrees in Denver and we only fell to 39 (but that's so cold for us!).
Here are some photos of frosty lettuce, the morning after a frigid night.
This was nothing to worry about -- crops such as beets, carrots, lettuce, chard, and potatoes can withstand a light frost. Hardy, cool-season crops, such as cabbage, broccoli, kale, Brussels sprouts and kohlrabi can even withstand a light freeze.
There is a widely repeated rumor that a cold snap can even make certain crops taste sweeter because of the sugar that's produced as a defense, but I am unable to verify this despite having asked a couple of expert farmers as well as Kathy Brenzel, senior garden editor at Sunset.
Warm-season crops (i.e. tomatoes, peppers, melons, cucumbers, eggplant) don't fare so well in the cold. Sometimes only the upper or outer foliage are damaged in a light frost and the plant may still continue to produce. You can take preventative measures to extend the season for warm-season plants by keeping them well mulched and covered if you know a frost is on the way. Cover plants or rows with blankets, tarps or floating row covers.