Yesterday I went out to ride and by the second half of the ride, my rear disc brake lever was acting up. Normally it doesn't engage till I pull the lever about a cm but it became Instant brake. Braking power wasn't effected though.

I don't know, maybe it is the Temperature. It was 25F yesterday but when I rode a few days earlier, it was no more than 20F. Yesterday there was a bit more fluffy snow on the trail though.

Any thoughts?