Mine has been experiencing this since the update also.  Very frustrating.  The only thing different for my series 3 LTE watch was that I had changed my weather app from Carrot to a couple others to try out.  The new ones were Forecast Bar and MyRadar.  They worked fine before the update.  After the update, I kept experiencing missing data and then the reboots.  Finally decided to reload Carrot to see if that made any difference (keeping the other two apps still on my phone/watch) but not using in any complications.  I have experienced no issues in the last 24 hours.  Hopefully it stays that way.