[wolffram]

If we think logically, it is not possible for the external humidity level to affect the internal workings of the watch which are sealed in an environmentally isolated compartment. Temperature on the other hand, which usually has a symbiotic relationship with humidity, definitely can influence the internal environmentally sealed workings. As with all amateur experiments there are many factors which are uncontrolled and definitely have an impact on the outcome. Without seeing the test environment my money is on temperature being the primary factor at play here.