I will tell you what the best science to date says but in my heart I wonder if science has really answered this question.
Huge study reported in the British Medical Journal in Dec of 2017. The researchers, out of Harvard Medical School, looked at over 11 million reports of people over the age of 65 visiting their primary care internal medicine specialist between 2008 and 2012. They scanned the billing codes to see if the patients complained of joint or back pain and then tried to see if those claims were more frequent when the local weather was rainy. They found no relationship between the billing codes and the weather.
I bet you can see the problems with this data. No matter how they tried to analyse the information, the truth is that unless you were there questioning the doc or their patients you can’t be sure that the patients had no increase in their joint problems when the weather was wet. Perhaps they had booked that appointment for other reasons and didn’t feel right discussing their aching bones with the doc. Or, had they self-medicated before the visit? Or, did they mention it but the doctor didn’t bill for it? You can understand how tough it is to find the answer to our scientific question by looking backwards in time in this way.
So for now, I’ll have to say that there is no strong scientific proof to support the belief that our joints and back are more likely to be sore when it’s about to rain or raining, but I will wait for better data before I change what my heart says about it!