Since Meteo's lead developer is currently busy and has little time to work on the program, a huge problem – the inability to search for and add new cities – has remained unfixed for a fairly long time. While there currently is no "official" fix to the problem, a member of the Meteo user community has come forward with a small "patching" application that will allow the search function to work again.
You can find this utility, called "Fix Meteorologist," at http://www.macupdate.com/info.php/id/24171. The Meteo team does not endorse this patch in any way, but we wanted to publicize it so that users (especially new ones) can use the app and not just give up on it (since it was essentially impossible to add new cities). A special thanks goes out to Diamond Software for coming up with the patch and making it available.