Weather/physics question

Weather/physics question

To all you smart people on this list I have a question: I live in northern Virginia, outside of Washington, DC. Last night the temps in my neighborhood dipped to 38 degrees F (I have an outdoor digital thermometer, that is very acturate). I noticed that some roofs and lawns had actual frost on them this morning. How can there be frost if the temp was 6 degrees F, above the freezing point? Respectfully, Flummoxed in Falls Church
My Container Garden picture…

My Container Garden picture…

what is it?

what is it?

Some deer have strange tastes.

Some deer have strange tastes.

tomato sprouts

tomato sprouts

Vern is looking good.

Vern is looking good.

Help ID’ing this plant

Help ID’ing this plant