Is the date and time of a full moon called the "offical full moon" or the definition of "pi" called the "offical value of pi"? So, why do so many call the Vernal (Spring) Equinox, which occurs today at 3:45 pm pdt (2245 utc/gmt), the "official" beginning of Spring. It is simply an astronomical event that defines when the plane of earth's equator passes the center of the sun causing the earth's axis to be perpendicular to its orbit around the sun. It is not a weather event and no one or no agency issues a proclamation making it "official" anyway.
And meteorologically, Spring is defined as the months of March, April and May.
Jan Null, CCM
Golden Gate Weather Services