When Is Spring Equinox 2025. In 2025, the official first day of spring is thursday, march 20. In the northern hemisphere, the astronomical start of spring, also known as the spring equinox, will occur on thursday, march 20, at 5:01 am edt in 2025.

The first day of spring (march equinox or vernal equinox) is when the sun shines directly on the celestial equator passing from south to north and the length of day and night are almost the same. The spring equinox, also known as the vernal equinox or march equinox, marks the beginning of spring in the northern hemisphere.