Thank your for reaching out to us! I can understand how adding this widget would be very valuable to your newsletters. Unfortunately with the editor that you are currently using we don't have a way to place a widget of that sort. What I would recommend is linking a button or an image to a web page that will showing them the current weather. You can click here to see a run down on how to accomplish that! I really apologize about the inconvenience! Please let us know if you have any other questions.
Thanks for sharing your workaround here! We hope other users find it helpful as well.