What region do you live in? “Weatherproofed” for San Francisco is very different than “weatherproofed” for Copenhagen. 
As far as the project itself, it may be pretty simple, it just depends on the exact shape of the bolt. In most cases you would just use a magnetic sensor so that when the lock was closed the sensor indicated one position, and when the lock was open it indicated the other.
Note that it doesn’t matter which side of the lock you are using as long as the magnet moves towards it and then away again. I just mention this because some locks have a turn bolt and it’s easier to capture the lock in its open position than in its closed position.
Anyway, the sensors have two parts. There’s the part with the sensor itself and the part with the magnet. You can use any magnet, you don’t have to use the one that comes with the sensor. And that gets themselves are generally quite weatherproof. So if you can find a small thin magnet that fits better on your project, you can usually use that.
Now it’s just a matter of figuring out how to mount the two pieces so that as the lock moves it will register with the sensor. Here is one example from someone who did this with an interior deadbolt. Again, there’s no networked control of the lock, just a sensor to say if the door is locked or not.
That is that with this type of sensor you could put a magnet on the very end of the deadbolt, but you don’t have to. Any place where the lock has a moving part can be used, including the Turnbolt.