Well, the ground radiates some heat, so that may be part of the equation when covering plants. In a hard freeze, it could actually freeze the water IN the plant, just like it does with pipes. We lost 15+ shrubs to that freak cold snap.
But I think if they’re not exposed to precipitation and it only hits 37, they might do find on the porch. Question is, then, can you afford the gamble?
If not, cover them or get them inside fo the night.