So over the last week two of the major weather information providers we use and rely on, Environment Canada and BBC UK Met, have changed the location of the XML weather information on their servers. This means that weather information has broken for people using Plasma widgets with them. We don't pay for the data, so we can't complain too much, but this is really poor behavior on their part in my opinion. Evidently we can't rely on online services maintaining any sort of day-to-day compatibility.
So how do we deal with this? Right now we have 4.3.0 coming out quite soon and it will have the new URL locations in it, and we'll backport those changes to 4.2 for KDE distributors to pick up. This is a short term solution and certainly not long-term.
Update: After some further digging, it appears that BBC's weather information has changed significantly in how it is delivered (split across two files now and using RSS XML). Backporting to the 4.2 branch will be trickier than just pushing an updated URL. :/
What we will be doing in 4.4 is implementing something that's been on our roadmap for a while now: widget and data autoupdates. We'll likely be using Get Hot New Stuff and DXS for this, and the packages will be cryptographically signed. This means we'll need to finally get that KDE gpg key rocking as well as a place to host these bits of data.
Personally, I'm thinking of hosting it on opendesktop.org as they are stable, reliable, have F/OSS as their focus and already run DXS services. That does mean that your Plasma would contact opendesktop.org every so often for updates, though we'll obviously make it configurable.
The end result will be widgets that don't fall out of date on you (if they are scripted) and things like weather data not suddenly stopping.
I apologize for the inconvenience in 4.2, and I ask for your patience and understanding as we work on complete and long-term solutions.