How to add temperature/weather forecast stickers on Snapchat

First you have to make sure you are allowing geo-filters:

1.go back to snapchat camera, click on your profile picture on top left
2. Tap on the Gear icon on top right to enter settings
3. Under "additional services", click Manage
4. Make sure Filters are on

Then you can add stickers.
1. Take a photo (it has to be taken by Snapchat camera)
2. Tap on sticker icon on the right panel
3. tap on the star on top
4. tap the temperature logo, it will be added to your photo
5. tap on the temperature again to turn it into weather forecast chart
6. Tap again to select F or C