Everything will be fine if planting is delayed!
Bareroot and pot-grown plants can be stored for a long time if necessary.
If bareroot planting is delayed in winter:
If your bareroot plants arrive and planting will be delayed for less than a week, open the top of the packaging leaving the roots in their bag and store them in a cold place out of the sun, ideally outside.
It doesn't matter at all if the weather is freezing, but you must not move the plants around when they are frozen.
If a week passes and it's clear that planting is delayed even further, consider "heeling them in" by digging a little trench, lying the plants on their sides with their roots in the trench and covering them with soil.
Heeling in is not essential, the plants will be fine in their bags, but it may give peace of mind.
Bareroot plants must be planted properly by March in the South.
Gardeners in the North can usually get away with planting well into April.
If pot-grown planting is delayed:
Simply put your plants in a sunny place and water them when the top inch of soil is dry.
This might be every day or two in a scorching hot mid-summer, but during a wet winter it usually isn't necessary.