Can cold temperatures be dangerous the first days after a FUE hair transplant? 5 days post-op.

Cold temperature is not "dangerous" after a hair transplant surgery. Unless it is so cold that other parts of your body is impacted.  

At 5 days post-op the outside temperature should have no effect on the grafts. Be careful with hats however, as anything rubbing the grafts side to side can dislodge them up to one week post-op.

If you wear a warm wool hat, it should be OK, but just use common sense and don’t stay out too long.  Be careful not to dislodge grafts as they are not completely permanent the first 10 days post-op.

The grafts are kept warm by the excellent blood supply to the scalp so going out into the cold should not harm the grafts. Wear a hat

The cold weather will not play any part in the recovery of your hair transplant. It is, of course, necessary for you to protect the area from the elements. A winter hat is a great option after 7 to 10 days. For the first week, make sure that you don’t wear anything on your head that may rub or disturb the transplanted grafts. A loose hoody shirt works well. It is also a good excuse to not have to go outside on a miserable winter day!