Well, we tempted the fates and it looks like we survived. After weeks of low temperatures in the 40's and sunny days, the weather turned to the north and we got a frosty blast on Monday. The low at our house was 26 degrees overnight. We knew it was coming from the weather forecasts but I was still a bit worried about your young little lettuce starts.
But G covered them up with reemay on Monday. That is a picture of the lettuce under cover at the top of this post. They made it! Yeah!
The weather is still cool but the lows are staying above freezing so that is a good thing. We are not totally safe yet. The last frost date is widely variable in my region due to the microclimates. Area closer to the water are usually towards the end of March. The UW in Seattle is March 22 but farther out it can be later. For example, Everett, north of me, is April 9th. We have had snow once in mid-late April. But usually by April 1 it is pretty safe. So I still have three weeks were we need to watch the over night temps.
Here is the garden under their blanket of reemay and what they looked like today.
Reemay covering the early lettuce bed - We also have two pots of blueberries.