Well, I am beginning to wonder the same thing.  I have RA and today I woke up and all the sudden felt much better.  My flare up was gone.  My sinus headache was gone.  The weather went from rain to snow.  Not sure how all this relates but I am wondering if my sinus infection caused the flare up.  All I know is I knew I hurt but didn't know I hurt as bad as I did until today when I woke up and felt better again.   I have also noticed over the last 24 hours I have lost a lot of fluid which tends to relate to when I am feeling better.  All things I have noticed over time.  I do seem to have flare ups around the time the seasons change.  Or even right before the big temp change.  This is year after year that I notice at the same time of year that I have flare ups.  All so odd.  I do wonder though if my sinus problem caused my flare up this time because I woke up today and the sinus pressure is gone and my hands are amazingly better.