Throw some steaks into the beds to hold the tarp over the seedlings. It should keep the heat in enough. I would remove it the next day if the temp heats up and the sun comes out.

Finally, all the seedlings you planted, except possibly the strawberries, should survive a light freeze or snow. In fact, sometimes snow acts as a good insulator for freezing temps.

Good luck!

I had the same question! My lettuce, onions, carrots, beets, sugar snap peas, potatoes, and strawberries have all sprouted and are doing well. We're in Owasso, OK and expected to get 1-3 inches of snow. I tried putting on some tarps, but the wind (G to 30mph) just won't allow them . So I put on some old sheets and just laid em across the top of my boxes and put heavy bricks on the sides to keep them anchored down. It was predicted to get to 32 tonight...but was just changed to 34 and also down to 27 Sat night. I'll check in the am and probably take off the sheets then put back on again in the evening.

Not sure if I'm doing the right thing either

http://forecast.weather.gov/MapClick.php?CityName=Owasso&state=OK&site=TSA&textField1=36.2801&textField2=-95.835&e=0

April