Depending on the portion of the globe you are at, the answer to the question will differ greatly. Astronomically, spring season starts on the day of the vernal equinox. An equinox is a day when both the day and the night have equal number of hours and there are two equinoxes in a year, the vernal and the fall equinox. As is normally the case with earth’s two Hemispheres, when one Hemisphere experiences the vernal equinox, the other Hemisphere experiences the fall equinox at the exact same time. Apart from marking the beginning of spring in the respective Hemisphere, the vernal equinox also marks the date when the North Pole starts to tilt towards the sun. If you are in the Northern Hemisphere, then the astronomical spring will begin on the 21st of March and if you are in the Southern hemisphere, then the first day of spring would be on 23rd September.
Meteorologists do not follow these dates as they are not the same for all the countries within an entire Hemisphere and also they are not practically accurate, which means that spring may come weeks earlier or later than what is marked on the calendar as the vernal equinox. In order to facilitate data recording and analyzing, meteorologists consider each season to start on the first day of a month and end on the last day of the third month. The meteorological spring of three months begin in the Northern Hemisphere on the 1st of March and in the Southern Hemisphere it begins on 1st September.
Spring is considered to be the most pleasant and desired of all the seasons by most and there are more obvious signs of spring season’s commencement. As the season begins, sunrises should occur earlier by roughly an hour. Also the sunsets should be set back by an hour adequately. Perhaps the most visible sign of spring is seen when one looks at the vegetation around, because the barren trees now start to develop lush leaves, flowers and fruits. The difference in temperature is of course another more obvious factor as the season is significantly warmer than the winter that just got over.