Hi!
Yes great question! As I have AxSpa and fibromyalgia like you, I can relate to what you describe in terms of different symptoms at different seasons.
Certainly in winter, I get more joints pain and muscles stiffness due to cold weather. Usually with heat pad, hot bath and stretching, I can manage 😉
In Summer, it seems to be related to my blood circulation which is not the best with the heat...I get swollen feet and legs, and I feel that can trigger pain and aches if it's too hot.
The ideal scenario for me is to have 20-25 degrees C all year long!!! And clearly, being in Scotland, I haven't picked the best destination for that. However with the global warming and current heat waves, I am enjoying our 25 degrees at the moment whilst it's over 40 degrees in my home town in France...
Take care,
Julie.