Winter comes with problems especially if the temperatures drop under zero. Everything freezes including your keys and locks. This is a major problem and if the door locks are old, the problem is even worse. Old locks have already collected too much grime and are possibly eroded. Keys are probably even slightly damaged. Such issues just make your life more difficult. When locks freeze, they shut out keys. In other words, customers won't be able to insert the key in let alone open the door. Clearly this would be the day you might experience a first house lockout and since the weather won't allow you to take a nice stroll in the neighborhood, its better customers know what actions to take.
Locks freeze because they are made of steel which contracts in the cold and so does the key. That's why we have such a hard time getting our key in the lock while our hands are frozen, too. That's also the reason why we hear that “cold clicking” sound when the key is trying to get in. The danger of a key breaking is high in such instances. That's why customers must be extra careful and gentle as they place keys in the security door locks. You should be gentle as you turn the key, probably have a hard time turning it, and in many cases find that it won't really turn unless you place force. Don't do it! It's best to work the key back and forth, left and right than breaking it.
Frozen locks are dealt easily with a hairdryer. The basic idea is to melt down the ice and as a consequence, you will require a heating source. So, if you are stuck outside your home, see if you have a lighter and whether you gain some results from this action. Heat up the key and work its way back and forth in the lock again and again. A good idea to avoid such problems and, thus, house or office lockout too is keeping the lock lubricated. You can do that even when the problem already popped. Once you heat the lock, spray some lubricants in the keyhole, and see if the key fits better. If the problem is not fixed despite efforts, it might be another problem, which may require lock repair.