PM Update: Scattered showers and thunderstorms through the early evening. Much cooler on Monday. You may have to dodge some raindrops through about 8 tonight. A cold front moves through tomorrow morning and ushers in much more seasonable weather.
Only cook live crabs, because they deteriorate very quickly after they have expired. You can simply throw the crabs in a pot of boiling water to cook them. Depending on the size of the crabs, it will take between 6 and 10 minutes for them to cook thoroughly. If the crab is alive when you start, the amount of cooking time has very little to do with safety  it s more a question of whether the meat is underdone, overdone, or cooked just right.
That means the legs do not need to be cooked for very long. To cook one pound of crab legs, expect to boil them for about 8 minutes. This should thoroughly cook the crab leg meat without making it stringy, tough or rubbery. If you want the legs undercooked and juicier, cook them for 6 or 7 minutes.