I'm having a bit of trouble understanding the proper operation of a cold frame. I've got one out in the garden now with a min/max temperature gauge.

Today, with a high of about 49 degrees, the temperature hit 100 inside the cold frame. That I understand, and I know I can vent it to keep it from getting that hot. But when I got home a couple of hours after sunset, the temperature inside was down to 32... exactly what it was outside. As I write this it's 29 outside and 29 in the cold frame.

It's been the same story since I got it a few days ago. It's exactly matching the outside temps at night -- and this is what I don't understand. Where's the benefit if I can't keep the "microclimate" inside at least a few degrees warmer at night?

Aside from trying to seal any cracks around the lid and throwing a blanket over it at night, I don't see an answer. And if I can't get home in time before the cold frame cools off... I can't blanket it in time to help.

Am I missing anything?

Thanks,

Rex