I often get questions from passengers who wonder how pilots fly & land in bad weather. Landing in bad weather is not hard. Landing in bad weather is called an instrument  approach because you rely solely on your instruments for navigation to the runway. On clear weather days air traffic controllers clear you for a visual approach which means you can see the airport visually from up to 35 miles & land safely. But, when the weather goes down then we rely upon the ILS, or instrument landing system. Basically,  this is just  simply a radial ,or a road that aligns you with the runway. The road is called a localizer. If you follow it then it will bring you straight on to the runways from twenty miles away. Along the localizer it also have three markers. One is the outer marker, the middle & the inner marker. Each marker serves as an identifier fix along the ILS so there is no doubt where the pilot is located on the approach. The ILS  also have a glide slope. Its provides vertical descent guidance all the way down to the runaway. By following both the localizer & the glideslope precisely then it should bring you down to a certain height called decision height or D.H. This height  for most ILS is usually 200 feet above the ground. To envision 200 ft it would probably be around the height of a two story building. When a pilot reaches the decision height, just like the name applies they must make a decision to either continue & land ,or go missed approach & go-around. For you to continue & land you must clearly have the runway approach lights in sight, & the runway. If the pilot can't see the approach lights then they go missed approach, & go around to try again or go to another airport. To get a look from the pilot perspective check out this video below.
http://www.youtube.com/watch?v=B2wuY5vTT80