just thought i'd add my experience.... 3 weeks ago i went up to the mountains to do some snowboarding. i've never before had my TPMS light come on. woke up in the morning and on my way to the slopes it lit up (constant on). i stopped the car, checked the pressures, all around 34, and continued on my way. when i was done riding for the day and driving back to the condo, the light went out. i've had this happen to me now 3 times. its on after a cold night, and off in the afternoon. i went up to the mountains a lot last year, and it never lit up then.... and it only does it intermittently to me now. the car has never been covered in snow, just in cold weather.
so, i dont know whats going on, but as long as the symptoms are always the same, i'm ok with it it... i guess