Post office workers usually start work around the hours of 6:00 AM to 7:00 AM to get the mail sorted and ready to be delivered.
Although the actual post office does not actually open up until around 8:00 AM the USPS workers are in the post office sorting mail and unloading trucks of mail.
Mail also travels during the night on USPS trucks to get to the post office.
The USPS sorting facilities are open 24 hours per day 7 days per week sorting the millions of letters and packages and loading them onto trucks to be delivered.
Usually the actual mail truck with the mail arrives at the local post office by 5:00 AM or even sometimes sooner and then when the workers are ready to unload the truck they will which is usually around 6:00 AM to 7:00 AM.
The mail carriers have to sort and case the mail for their route and then they usually start their route by 8:00 AM to 9:00 AM.
However some mail carries I see out in some areas around 1:00 PM and continue delivering until 5:00 PM and sometimes later if they have a lot of packages or mail to deliver.
USPS comes to your house or address to deliver mail at around the same time everyday.
However there's not exact time that the USPS comes to your house or address to deliver your mail to you.
In my experience though my mail carrier always comes to my curbside mailbox to deliver mail between 9:45 AM to 10:30 AM.
So the time can vary depending on how much mail they have to deliver but most times the mail does come around the same time everyday but not always.
A Mailman or mail carrier can refuse to deliver mail because of snow being on your porch, near your mailbox on your sidewalk etc.
It's your responsibility to keep the path to your door and mailbox clear so the mail carrier or mailman can safely deliver your mail.
If you have icy sidewalks, icy conditions that could make it so the mail carrier can slip and fall then they can refuse to deliver the mail to you.
Rain does not affect mail delivery unless the rain is causing flooding conditions.
If it's just raining then your mail will still be delivered but if there's flooding conditions then the USPS will have to stop mail delivery to the area that is flooding until the flooding resolves.
But normal rain does not stop or affect mail delivery.
USPS does deliver in snowy and icy conditions as long as it's safe to do so.
There have been rare cases where USPS had to stop delivery due to blizzard or very snowy or icy conditions because it was dangerous for the USPS carriers and workers to be out in the snowy and icy conditions.
If it's really bad out and the roads are really icy then the USPS may have to stop delivery of your mail for a few days but it's rare that happens.
Sometimes there may be a temporary delay for a few hours while the roads get cleared and deiced.
But USPS will make a very good attempt at delivery of your mail and packages even when it's snowing or icy.
Not everything shuts down when it's snowy or icy and the USPS will deliver in snow, rain, ice, wind etc.
I've had a few USPS deliveries not arrive for a few days when the weather was really snowy but that does not happen often.
I want the USPS workers and everyone else to be safe so I can wait for my mail and packages.