Honestly, I don't consider rving in harsh weather conditions to be extreme rving. People live there year 'round - not a big deal.
Extreme RVing, for me, is going places and doing things most people can't or won't do. Around here, it is mostly found in the TC forums or sometimes in the boondocking forums. There are no forums here for Europe, Asia, South America or Australia which I think would be more extreme than Tempe, Az, regardless of the weather. Boondocking on a Baja, Mexico beach or Nabesna Road in the Wrangell's is a little more extreme than Bellingham, MA.