For me it's the barometric pressure thing. Low pressure causes me pain, not low temperatures. I like winter just fine. However, I am humidity intolerant as well. I don't mind hot, but hot and humid I do--and mind it much more than cold and humid.
As to the thing about fibromyalgics who've had it longer not minding the weather...it may be that the chronic pain has in some way desensitized us to the minor pain changes associated with weather and folks who are just 'getting' fibromyalgia are still pain sensitive. I know now I've been fibromyalgic for probably more than 20 years. I've made a LOT of improvement thanks to diet changes, regular chiropractic care, and weekly massage sessions (plus all the supplements I take). If there was just SOME WAY to stop the adhesions from forming I'm SURE the symptoms would go away. I personally feel it's the ADHESIONS/LESIONS that are the CAUSE, not just a symptom. I believe this is some kind of autoimmune disease where our bodies are contantly trying to form scar tissue. Just MHO.