The spring equinox (around March 20-21) marks the astronomical beginning of spring, when day and night are nearly equal in length at approximately 12 hours each. Following the equinox, the Pacific Northwest gains about 3-4 minutes of daylight each day, creating a rapid acceleration toward longer days. This balance point has been celebrated by cultures worldwide for millennia, and in the Pacific Northwest, it coincides with explosive spring growth and migration activity. Watch for the greening of deciduous trees, the opening of countless wildflowers, and the peak of spring bird migration. The equinox triggers phenological changes throughout ecosystems, with plants and animals responding to increasing day length as much as to temperature. This astronomical event serves as a reliable marker for the transition from winter's dormancy to spring's exuberant growth.