Plants including Daylilies bloom at very specific times which only vary depending on the season's progression. A late spring, a cool early summer or lots of hot dry weather can effect the blooming timing of daylilies. Additionally, these seasonal variations can effect fruit and vegetable bearing.
Using Daylilies you can get a sense of how your season compares to other seasons and how it compares to other climate zones.
Stella D'Oro: Blooms here in Vermont in late June. Considered to be a marker for the beginning of the early season.
Here Olallie Early Snowfall blooms along with Campanula glomerata (Bellflower) the two always bloom in conjunction (around early July).
Here H. fulva blooming away at Olallie Daylily Garden July 12, 2015. The H. fulva has not yet bloomed here in Vermont for 2016