I've always felt that a screensaver should be useful and attractive. Clear Day Screensaver for Mac is both. This US$1.99 app lets you view the weather in more than 2.5 million cities via a beautifully rendered globe. Information includes the current weather, three-hour predictions and the forecast for the following day.
Clouds are also accurately displayed, along with the current time in either 12- or 24-hour format. Temperature can be displayed in Fahrenheit or Celsius.
I gave the app a spin on my Mac Pro with a 30-inch screen. Animation was smooth, and the forecasts and current conditions displayed matched up with other information I found from typical sources. I searched for some more obscure, small towns which the app found via ZIP code or name. Clear Day Screensaver supports English, French, German, Italian, Japanese, Russian and Spanish.