A social worker whether a CPS worker or Adult Protective Services Worker can show up and turn up unannounced.
Social workers usually do turn up unannounced to catch people off guard.
They don't want to give you notice so that you would have time to act differently or leave the area.
One social workers get involved then you can expect them to show up without notice at anytime of the day even on Saturday and Sunday and sometimes Holidays as well.
Although if child welfare caseworkers pay you an unannounced visit, you can ask them to come back at a better time.
Caseworkers have rights and authorities that may override yours.
The DCP&P can get a court order that will grant them the legal right to enter your home and even take your child.
But without the court order you can ask them to leave and come back later.
Never allow the CPS or social worker into your home without a court order.
If they have no court order then simply ask them to leave.
Don't let them scare you with threat of arrest because even if they call the police they still can't force themself into your home unless they have the court order or warrant signed by the Judge.
That is unless the child is in danger right then and then in those cases the police and CPS can take your child without a warrant.