My 2015, 40k miles, has tire sensor warning lights activated any time it rains, snows, drops below 50F, etc.

Dealer won't replace because there is no fault showing. 

Checked pressure... to spec. 

I live in Colorado...9 months of the year the sensors want to go off. 

1.  Solutions?

2.  How to make dealer replace them?

I've got a 2014 X1, I think it's on 225/45R18's, but don't quote me on it. 

Only ever had two warnings from the TPMS, both wrong and reset normally. Temps here are anywhere between 20 to 90 deg f. Also frequently wet and snowy etc. The warnings I have had have not been weather related. 

I don't know how much the sensors are but it may be worth changing them but I guess only 1 may be faulty, does the readout indicate it's the same tyre every time, if so just change one. 

I also take it you're on an extended warranty over there but that's no use if they aren't listening to you. 

Upt'North.