Thermometer is a very simple utility that displays the temperature on the menubar. Unfortunately, that is all it does, which makes it a very weak application. I was expecting this one to have automatic location updating, but that feature isn't included either. You have to manually add the cities that you want the application to retrieve weather information for. You do this by clicking the "+" sign on the application's main window. There doesn't seem to be a limit for the number of cities that you can add. Only one of those can be displayed on the menubar, though, and this is simply done by checking a button next to the location that you want to put up there.
When you click on the menubar icon, a small window will pop-up which shows all the cities that you have added and their current temperature.
Thermometer gets its weather information from Weather Underground, which updates information for around 29000 locations around the world. I added two locations and the temperature seemed to be accurate.
The time at which the temperature for your location was updated appears at the bottom of the window, and you can manually refresh it by clicking the button on the left.
To sum up, Thermometer works as advertised but I can't really recommend it because there are so many applications out there that are way better than this one. Still, it is free, so you can go ahead and give it a try if you want.