UPS will work in snow and any conditions to deliver packages as long as the weather conditions are safe enough for the UPS drivers to drive and deliver in.
For just a few inches of snowfall the UPS will still deliver packages in the snow but if a major blizzard happens or major snow event that makes the roads hard to drive on or impossible to get through then the UPS driver will stop deliveries until the snow clears up.
UPS will put notifications on their website at the top of the website showing if deliveries in your area are temporarily delayed.
As long as the snow is not too deep and the roads are clear the UPS will deliver packages.