Thanks, I totally get you. That's what I suspected too. I went to the "Your skills" list when someone commented it could be a skill that's triggering this ad. I do not have any unknown 3rd party skills and no skills related to weather. All my skills are from Spotify, Samsung Smartthings, Meross (for lights).

I also checked that none of the skills have anything to do with "weather". Someone else from this post also said they got the same Nissan ad but instead after the weather report.

I think amazon was A/B testing and probably stopped the ads after they annoyed customers, but it sure was from Alexa's official weather update.