I read some place that fibro effects the cartilage that attaches ur muscle to ur bones. When they get damaged scar tissue builds up and it doesn't heal properly so when it rains mainly it feels like ur joints hurting. That cartilage becomes tight making it hard to move the joints on daily basis. I hope this helps.
I've been tested for arthritis and test came back fine. Yet every time it rains I feel like a rusty tin man. And snap crackle pop every joint. Most bones hurt. So I did some research and discovered that.

Thank you JessM I too was tested and they came back negative however I still have cracking and creaking in my joints... I recently found out however that my hypothyroidism is the culprit or is at least adding to the problem...

I experience the same thing, and had the problems before I was diagnosed with FM.

I would ask your rheumatologist and I would also ask them to check you for arthritis

I click and creak in most joints. It's terrible.