I remember using WeatherEye for the BlackBerry back in the day, and now is available for the BlackBerry PlayBook. The application looks really nice it comes with popup weather alerts. Some of the options include choosing from Fahrenheit or Celsius. Allows you to set multiple cities perfect if you plan to travel to see the weather to the place you are visiting. It also allows you to view current weather, hourly, short and long term. The interface looks nice it is a bit slow in response but overall it provides good information.
To download check it out at this link.