I think I may know what’s been happening. As it turns out, you should make certain to have ONLY A SINGLE WEATHER APP installed on both the phone and the watch. My SO had multiple weather apps and when she had the watch set to mirror the iphone it was connected to, it seemed to be getting confused maybe because it was polling from multiple weather apps. Those weather apps were also mirrored on the Watch. I set it to Apple’s weather app and all has been fine ever since.
By the way, once I deleted the other weather apps from the phone and then on the watch toggled off the setting for Apple Weather under the Watch’s “Background App Refresh” setting, waited 15 seconds then toggled it on I turned the watch off then rebooted the iPhone and logged in. I then turned the watch on and it’s been steady ever since.