Important Note: Unfortunately the Weather Underground API no longer has a free version. More info here.

In the end it will look something like this:

STEP 1 - GET WEATHER

• Import the Weather Underground API in AutoWeb and enter your API key. More details here.
• In a new task add an AutoWeb Tasker action
• Select the Weather Underground API
• Select the Forecast action
• Check that the Query has a default value of %LOCN and Language a value of English
• Enable the High Celcius, Icon URL and Low Celcius outputs
• Accept the action and add a Flash action with the text %highcelcius() %iconurl() %lowcelcius()

STEP 2 - SHOW NOTIFICATION

• Add a new AutoNotification Table action
• Set the Title to Weather
• Set the Texts to:

Code (Text):

%highcelcius()
%iconurl()
%lowcelcius()

Make sure to use the new lines as shown above because that's what will let AutoNotification how to correctly show the table.

• Set the Row Separator to a single new line. This will make AutoNotification know that each line is a list of cells of a row in the final table
• Set the Cell Width to 50
• Set the Text Alignment to Center

If you now run the task a cool table notification with the weather for the next 3 days will be created!