The comment about needing a porch roof or overhang or awning is right on.
However, there are a few things you can do - I have a front door that used to be recessed about 3 feet into the house face but had a tiny entry area, so I pushed the wall and door out flush, and have not yet gotten around to installing a porch roof (this summer maybe ???). Mine has gone about 5 years without a drop of water getting in and zero dampness in the sill wood, with three simple additions to the standard door - these are all things you can do yourself, though the bottom seal requires taking door off the frame to install with some types that screw into the bottom so you don't see screws on the face:
1) drip edge over top of door -
2) bulb seal and drip cap under door (2nd diagram, fits on bottom of door) -
3) bulb type weatherstrip all around sides and top of door frame -
that article shows simple stickyback foam strip - the bulb type works better, but may require striker adjustment due to its thickness.
IF you are planning on putting in a storm door, do that BEFORE the drip cap and door foot drip cap, as not all will fit with all storm doors, especially if the storm door fits inside rather than over the frame. Of course, with a storm door then you should not need the door foot cap, though the under-door seal is still important.