From a plant's point of view, late summer and early fall is a good time to plant.
Most woody plants require less moisture late in the growing season.
In spring, plants have succulent new growth that needs water to be kept alive. Cool soil temperatures in the spring are responsible for slow root growth. Spring rains wet the soil and also slow the warming process to a degree where root activity is strong enough to support a newly planted tree or shrub. Late summer and early fall weather is usually well-suited to plant establishment. Shorter days, cooler outdoor air temperatures, and more rainfall provide an environment that results in less water loss from plants and more abundant soil moisture.