There are some psychological encouragements and deterrents associated with gardening, especially in the Springtime.
I realize that phenology reflects immediate past weather as well as plant intensions but observed, local cycles of plant life can be helpful. Several events serve some guidance for me.
Oregon grape is very common in this area. It is native and growing in our nearby, lower elevation forest as well as in home landscapes and parks. Oregon grape's bright yellow blooms begin to open while some frosty nights can still be expected but it serves as a guide for my garden pea planting.
Black locust trees can be considered an invasive but it is common and seems to be thriving. There is a location that is one of the very earliest sites of a European American settlement. There is almost what might be considered a black locust forest there. After those trees have leaves from lower to highest branches, I have only seen one time over many years when a late Spring frost has occurred.
Steve, who would use "When oak leaves are the size of a squirrel's ear" for a guide if he knew which variety of oak and if gray or fox squirrels are being considered.