It started 3 years ago. I contacted Sirius two years in a row. The first time they walked me through the menus to turn it off, and it worked. The second year they said it couldn't be turned off and that I'd have to wait for the promotional period to end (see below), so I filed a formal safety notice at nhtsa.gov, but never received feedback.
The alert pop-ups keep blocking part of the navigation map until I press the damned Dismiss button while driving in order to see the full map. Repeatedly pushing the Dismiss button distracts from driving, and so is a safety hazard.
I was told that every November Sirius gave out a few weeks of free service to help promote the service. But that caused the useless and repetitious wind alerts. I live in a naturally windy place such that wind alerts are superfluous; it would be comparable a North Pole freeze alert.
It happened again this year, but I was fortunately able to switch it off via settings menus. I don't know why deactivation is different per year. I suspect they do it to get people to poke around in the menus and see the different genres of music & talk channels they have, hoping to entice sales. It's probably stealth advertising disguised as a defect, or a defect they leave in place that happened to improve sales, so is ignored.
F$CK YOU SIRIUS!