I say something in my manual that my clock is set to the Ottawa Weather Network, and to please make sure that yours is set as well.
Never had anyone come early. If someone did, I would refuse to open until my set opening time. You don't see a grocery store open just a few minutes early because people are banging on the door, do you? Same thing goes for me...I am a business as well.
I've had people come late for pick-ups and it's usually when I need to get somewhere, as in an appt. They are charged my late fees.
IF they call or text me in ample amount of time saying they are running late because of construction or weather conditions, I'll give them a 5 minute grace period. BUT...they have to understand that I have hours of operation for a reason. I have a life too!