Deviations In Phenology

Day 123: I have been thinking that the pussywillows seemed late this year, but checking my phenology notes (i.e., posts and photos), I see that catkins have emerged as early as December 22, and as late as March 16. That strikes me as a pretty wide range of deviation. My weather records show nothing remarkable for that early year: not overly dry or wet, no prolonged hot spells or unusually cold temperatures, although the summer was smokier than usual due to wildfires. Could that have instigated an early bloom? Could the tree have been stressed by aerial pollutants to an extent which kicked it into survival mode? It's an interesting hypothesis, and I suspect it's one which will lead me down a rabbit hole later on today as I try to find supporting documentation. In any event, the pussywillows are right on time according to my logs. I was just overly anxious for them to appear.