How fast is United States Postal Service Shipping?

I would be shipping something in an envelope tomorrow morning on Wednesday from NY using USPS. Can it get to California by Friday? And if so, what option do i need to choose? Is priority good enough? How long does that take?How fast is United States Postal Service Shipping?
With the usps one can never be sure of time. One article may get there in two days, and another might take a week.

I mailed my son, 400 miles away a package by priority mail, took seven days, where another package just mailed regular parcel post only took two days,

You can of course get a guaranteed delivery, but at much higher cost.How fast is United States Postal Service Shipping?
I would go to the post office and ask them. You can pay extra to get it there by Friday, but I would think it would get there if you mail it tomorrow without paying extra. I can mail something to my family after 2 and they get it the next day when they live 3 hours away.