Just figured this out

I’m sure this explanation is available on Google, but I figured it out for myself and I’m proud.

Often I’ll see frost on roofs and other surfaces when the outside ambient is about 38. The previous day was up in the 40s or 50s, and there was no actual freezing in recent days. Why do some surfaces get frosty?

Now I’m seeing the same oddity when I pre-process fresh food so I can use it quickly for each meal. I strip the florets from broccoli and cauliflower and chop carrots into small pieces, then toss all of this in an open bowl in the fridge. I then grab a few handfuls of this mix to cook for each meal, along with other stuff like canned soup or ramen or tomatoes. The ambient in the fridge is 38, and the carrots have never been in the freezer. The carrots are always frosty. They stick together as frosty things do.

Figured it out. Modern fridges don’t simply absorb heat through the walls into the coils. Modern fridges blow cold air over the food, and the cold air is below freezing in order to absorb the heat and end up at 38. The same thing must happen outside. When the ambient is being pulled down to 38 at sunrise, it’s pulled by below-freezing air currents, which are then distributed and mixed with the existing 40s to end up at 38.