I'm in the middle of Kansas, in the middle of the lower 48 states. Usually winters are some days and nights above freezing alternating with days and nights above freezing, and lots of above freezing days and below freezing nights.
Last year was unusual in that the whole winter was unusually warm except about a week in February with unusually cold, below 0 F, day and night.
That killed a lot of plants that would have been OK if those low temperatures had come on less suddenly.
So this year has been, for here, unusually warm weather/ I have about 300 Ponciris and Citrus x Poniris hybrids under lights. My lights aren't quite as good as I would like. So I've been putting the seedlings and parent plants outside on warm days and bringing them inside when freezing temperature are predicted. So far the plants all look healthy.
I doubt they are growing as much as they would in a warm room with good light, but they are doing OK. I think the short winter nights are reducing their growth.