Yahoo's weather app, which was revamped on the Droid platform recently, seems to be part of a bigger "revamp" of all things run by Marissa Mayer (their CEO). Other parts of Yahoo's PC realm have been altered quite a bit over the past couple of days, including the weather page.
Instead of getting a basic white background and your temperature and forecast, and ad placement, Yahoo! is blending in Flickr images (much like the app does) that would blend with the time of day and the particular location that you're browsing for weather conditions in.
I normally don't rely on Yahoo's weather for part of my daily browsing (I only stumbled into the changes after seeing Yahoo's sports page get completely revamped) -- but there are people who do...and those who were used to the old look were probably surprised by the new appearance of the site. Content hasn't changed much -- weather is weather -- but the look and feel of the page is more in line with their app (which I am more familiar with) than it was prior, much along the same lines of how Google Now's weather card works in synergy with one simply typing "weather Philadelphia" on any random Google search.
The weather information on Yahoo's page and app are powered by The Weather Channel, which have their own app and forecast pages as well. So much for avoiding duplication.
More info on the revamp...and the promise of more ads on your Yahoo pages...is available in this article.