What better place for a weather app than your menu bar, allowing you to see the current outside temperature with additional details available at a click. One simple, but effective weather app for your menu bar is WeathrClip by Gavin Wiggins.
WeathrClip sits in your Mac's menu bar, displaying the current temperature along with a weather icon that reflects the conditions outside. Tapping on the icon displays a popover that contains the current weather conditions, a four-day weather forecast, and an animated radar with details from your current location or a specified location.
Weather data is pulled from Weather Underground and arranged so you can digest all the important weather details in under a minute. WeathrClip's layout may not be stunning, but it is functional and to me, that is more important overall. Personally, I prefer WeathrClip to the web version of Weather Underground as I find it easier to just click on my menu bar instead of opening a web browser and navigating the Weather Underground site.
WeathrClip has a handful of options that allow you to add multiple locations, change the weather refresh time and the units for your temperature. There also is the ability to store favorite locations, manually refresh the data as needed and change the Wunderground maps information.
WeathrClip is US$1.99 from the Mac App Store.