- There are no long-term trends in the severity of pollen seasons over the twenty-year period.
- Tree pollen seasons can start anywhere between January and March, usually peaking in April and ending in May.
- Grass pollen seasons usually start during May, peak in June, and end during July.
- Pollen seasons that start early tend to last longer.
- Pollen seasons that last longer record more cumulative pollen, rather than spreading out the total pollen count.
- The severity of tree and grass pollen seasons are loosely correlated, suggesting that there may be a correlation between the start (and duration) of a tree pollen season and the subsequent start (and duration) of a grass pollen season.