Albeik's Weather 0.51 docklet does not work properly with the latest RK Launcher 0.41 beta build 111 (nightly build) and the same problem appears with the latest regular build 0.4 beta 186.
The problem is that while docklet technically works, it doesn't update weather information automatically. You have to right click on the docklet icon and choose "Update Information" every time you want to see the current weather update, otherwise you are stuck on the same display you get when you first run RK launcher.
This problem did not occur with the earlier RK Launcher 0.4 Beta 149 that I was using for a while.
Here's the URL to this docklet:
Aqua-Soft Forums