@galfert
Weewx's windy extension takes an ID as one of its inputs along with the API Key.
It's that ID that I was referring to, it's neither the public station id nor the API Key.
The info part parameters of the protocol at the top of this topic also lists a station (alternative names: si, stationID) as one of the parameters.

@TomSlavkovsky
stationId is listed a 32 bit integer but on the station information screen and on windy an ID is shown in what looks like hex.

It's confusing for users who are configuring uploaders, they need to use an integer and that integer is not the id listed on the configuration page it's 0,1,...