Originally Posted by Tumeg

CONTEXTS:

• Time; 00:00 to 23:30 - repeating every hour.
• [You can also have a context for battery life, so if your battery gets too low, it will stop checking the weather and what not]

TASKS

• Variable -> Variable Set: Name: "%ZIPCODE" - Then in the "To" field, put in your zip code.
• Net -> HTTP Get: Port="rss.accuweather.com/rss/liveweather_rss.asp?metric=1&locCode=%ZIPCODE"
• Variable -> Split Variable: Name: "%HTTPD" - Splitter: "Currently:"
• Tasker -> Stop: If: "%HTTPD2" is NOT SET
• Variable -> Split Variable: Name: "%HTTPD2" - Splitter: ":"
• Variable -> Variable Set: Name "%HTTPD21" To "Sunny" If "%HTTPD21 ~ *Sunny*" (make one of these tasks, for every weather type you intend to encounter. i.e "Sunny" "Rain" "Storm" "Cloudy" "Clear")
• Variable -> Variable Set: Name "%HTTPD21" To "Default" If "%HTTPD21" does NOT equal "Sunny/Rain/Storm/Cloudy/Clear"
• Variable -> Variable Set: Name "%HTTPD21" To "Night" If "%TIME > 20"
• Display -> Set Wallpaper: Image "wallpapers/%HTTPD21.jpg"

To make this work, just have a folder in the root directory of your phone entitled "wallpapers" which will contain each of the wallpapers. Title each wallpaper with the corresponding weather that you have in your tasks (I believe it is case sensitive).
The "Default" one, just is a basic wallpaper that will be used, if none of the weather conditions are reached. The "Night" task\wallpaper, will be used after a certain time (In the tasks above, it will start at 8pm)

Original Source: Weather Dependent Background Image - Tasker Wiki