Seasonality Core 2.0 is a Mac app any weather aficionado should have. That's because it's probably the most complete and detailed weather software I've ever seen on the Mac. The interface is simple enough. A list on the left allows you to enter any number of cities around the world you want to track. It's got 34,000 built-in cities in more than 200 countries. Additionally it allows you to add custom locations using ICAO stations, latitude and longitude and more.
A selected city's forecast is displayed at the top of the app along with its current temperature, wind speed, cloud cover, dewpoint and more. To the left of the forecast you'll also see information about the length of daylight, sunrise and sunset times and the local time. But those metrics are something you can find in most weather apps.
What sets Seasonality Core apart from the rest are its interactive graphs and amazingly detailed maps. The graphs, which chart a location's temperature, wind speed, wind direction, cylindrical wind direction, pressure, participation, snowfall, cloud cover, humidity, and wave height, not only show you the next seven days for all those metrics, it allows you to see a history of those metrics going back day, weeks, month, or even years. But my favorite part of Seasonality Core are the maps. They're beautiful. The terrain maps aren't actually Google Maps (for once). And they're available in over 2 gigapixels of resolution. More so, they're dynamic, meaning the terrain images change every month so you can see the turning colors of the leaves or the snow line move across the earth.
Like any good Mac app, Seasonality Core has been designed for optimized OS X Lion use. The app offers fullscreen view and also multitouch gesture support for the graphs and radar/satellite imagery.
With all the data sets and features Seasonality Core offers, it probably not even appropriate to just call it an "app." It's like having a full weather center built into your Mac. Seasonality Core 2.0 is available in the Mac App Store for US$24.99.