One of the coolest features included in Android 4.1 was the enhanced notifications. If an app supports the feature, you can swipe down and expand the data being shown. Many of the stock apps do this, but third-party developers have been taking advantage as well. Notification Weather offers its own twist on notifications by adding rich weather forecasts to your Jelly Bean device's notification shade.
This app's notification comes in two forms. The first is a single line with the current conditions. The other is a two-line block with the current conditions and a 4-day forecast. You can choose in the settings what units you want, how often it updates, and whether it defaults to the expanded or collapsed view. Like many apps that utilize ongoing notifications, Notification Weather uses a persistent icon in the status bar, which bothers some people.
Notification Weather is free in Google Play and it's very clever, so it's definitely worth checking out. You will need to be on Android 4.1 or higher to run it, though.