Regarding your question on cottonwood seeds this year, I was unable to find specific information to explain a longer than usual seed shedding.  Cottonwood trees produce a lot of seeds every year, but they do have what they call mast seed years every 3-4 years where a larger quantity are produced.  Also, the seeds are ready for shedding general by the end of May at latest and can continue releasing all the way through June and early July.  However, the typical length of time is 2-3 weeks.  As trees mature over time, they produce more seeds.  The articles below provide more information about cottonwood trees. 
https://bygl.osu.edu/index.php/node/2158
https://ohiodnr.gov/discover-and-learn/plants-trees/broad-leaf-trees/eastern-cottonwood-populus-deltoides
For your question on whether we have seen earlier blooms this year than typical, the answer is Yes.  The phenology of plants uses Growing Degree Days (GDD) to predict the timing for various blooms, insect emergence, etc.  GDD represents an accumulation of daily temperatures that affect the soil temperature, etc.  The articles below share more information about GDD, including the ability to compare year to year.  In looking at the second link which provides the specific calendar of GDDs, I checked June 10th of 2022, 2023, and 2024 in Wooster, OH.  The numbers respectively were 825, 687, and 919.  Given that the number is higher in 2024 than the past 2 years, you would expect to have seen earlier than usual blooms even vs recent years.  In general, growing zones are getting warmer as the climate is warming on average, although there is significant fluctuation year to year.   
https://bygl.osu.edu/node/2311
https://weather.cfaes.osu.edu/gdd/CalendarView.asp
https://www.usanpn.org/data/maps/AGDD
Hopefully this information helps answer your questions.