I do not know if FM/CFS or Osteoarthritis react differently for different people. Climate change does seem to affect everyone. As for me, if the Barometric Pressure gets to 30 points and above, my body begins to flare and continues till the barometric pressure goes back down to below 30. I do feel so much better in the heat and humidity does not seem to affect me. For me, mid August our summers ever so slightly begins to progressively get colder. The cold of winter months really affect me adversely.
For laughs I Googled "Where in the United States does the barometric pressure fluctuate the least?" It responded, Honolulu, Hawaii and San Diego.
Wishing the best to everyone. I hope the sun shines on everyone and keeps you warm. Many Blessings.