I reviewedSeasonality Go (US$5.99) a couple of years ago when it was an iPad-only weather app and pretty pricey at $10.99. I liked the app, but wished for a lower price and an iPhone version.
Those wishes have been granted, as the app is now 40 percent cheaper, and has a first class iPhone version. There are plenty of free weather apps, so you'd wonder what makes this app worth putting money on the table.
First off, there is a wealth of information here: 30,000 weather locations in 200 countries, and astronomical data like sunset/sunrise time and moon phase. There are graphs for 10 weather variables including temperature, wind speed, precipitation, cloud cover and more. There is an animated satellite map with radar and infrared weather data. This latest version has been thoroughly rewritten and adds even more data like dew-point temperature graphs.
My favorite feature is the Particle Mode. It simulates what you would see if you dropped some confetti into the air and watched the patterns as it blows. You can watch in a worldwide view and see major weather systems, or zoom down to your location and see the wind direction or how the winds interact with weather fronts.
Maybe it's more weather data than you think you need, but you will get used to the richness of the data and the striking GUI. This latest version has been optimized for the iPhone 6 and 6 Plus, and it really looks clean and easy to read.
Most people won't buy a weather app and are well served by freebies like Yahoo Weather, but if you crave more, Seasonality Go is really worth a close look and your consideration. There is built-in help and good explanations of what you are seeing.
It requires iOS 8, runs in both landscape and portrait mode, and to me it is worth the investment. Check it out on the app store and see if it catches your fancy.