I know not all Mac users take advantage of the OS X Dashboard widgets; some even claim that it's time Apple does away with it altogether. But I use it quite often to track packages, and view current weather conditions through the stock Weather widget.
Getting to the Dashboard isn't always convenient, so adding a menu bar icon to detail the current temp and weather conditions seemed like a good idea when I came across Degrees in the Mac App Store.
The free app doesn't offer much in way of features, but it doesn't need to. When you launch the app after installing, you'll see a weather icon in your menu bar with the current temperature outside. You can enter your location, or let the app determine your location for you. You can also limit it to displaying only the current temperature or current weather conditions if your menu bar starts feeling a bit cramped.
I did have some issues entering my location, and the first go wouldn't let me select the box for Degrees to determine my location for me, but quitting and relaunching the app resolved both issues.
You can download Degrees from the Mac App Store for free. It's compatible with OS X 10.6 and up.