This might be the silliest sensor available given that the only valuable part here is the PCB with the winding traces and that all the controller does is to pass a weak current (for the sake of efficiency) through the two poles of the PCB and hopefully make contact between the two intertwined traces if there is some water or snow on top of the traces to make contact.

In principle, you could create a such a sensor or even better just using copper wires and literally just passing current through and draining the current into a GPIO pin ( or depending on the voltage tolerance of the controller); then, iff. the GPIO pin measures any non-zero value, then the circuit is connected and there must be some rain or snow between the wires, or otherwise, if the GPIO does not measure any value there is no rain or snow.

Like many other cases, this is one sensor that does have an analog output but the actual analog value being read does not really have any special meaning. In fact, the higher the value, "the better the contact", but that does not necessary imply that there is "more rain" or "more snow" - it could just as well be a large pigeon dropping on top of the circuit that makes great contact. On the other hand, it is a good "learning sensor" and one that can be reproduced easily, as mentioned before, without even having to buy anything special.