The weather and the change in the barometer can cause an immediate flare up.

Yes, One day feeling good, out and about. Next day, can't get out of bed.

Rain does affect me too, weakness, all over increase in pain, exhaustion at its peak, but the barometric pressure and humidity levels seem to be high when rain has such a drastic affect on me.

I live in South Louisiana and live with this type of flare up almost constantly during the summer months due to frequent, sudden rainstorms. When it happens, I usually have to go lay down as I become too weak to function along with the pain.

Same for me - feel OK one minute and then wham, it changes the next minute. Weather is a huge factor for me.