Certified GKH Gardening Expert
Generally, in zone 10 where they are hardy, you can plant them at just about any time, once the temperatures remain above 65-70 degrees, though. The rest of the US north of zone 10 needs to wait until mid summer to plant, since the temperatures at night will stay below this for quite awhile.
They really like it hot and dry. They are very drought resistant and prefer high temperatures.
This article will help you to care for them: https://www.gardeningknowhow.com/edible/vegetables/sweet-potato/grow-sweet-potatoes.htm