Recently I heard a PSA on the radio regarding the need for listeners to ensure that their house address numbers are clearly visible from the street in case emergency crews (paramedics, firefighters or police) needed to respond to a call for assistance.
I second this message. When you call 911 to request an ambulance, you don't want the ambulance crew to have to spend extra time circling in the neighborhood or going door to door to try to figure out which house is the one with the person who needs assistance.
I am a retired California police officer. I spent many years responding to calls and looking for addresses. Too many people rely on 1-inch high numbers peeling off their mailboxes to indicate their address.
I can't emphasize enough the importance of having house numbers large enough to be easily seen from the street and mounted on a high-contrast background (i.e., dark-colored numbers on a light-colored background or vice versa) unobstructed by foliage or architectural elements such as exterior light fixtures.