Spring is one of the four temperate seasons. Spring marks the transition from winter into summer.According to an astronomical definition, spring begins on the vernal equinox (usually March 20 in the northern hemisphere) and lasts until the summer solstice (usually June 21 the northern hemisphere). According to this definition, therefore, the traditional midsummer's day is the first day of summer. The meteorological definition (used in order to express whether 'spring' has been hot or cold or wet, for example) has spring starting on March 1, since this is more in line with weather conditions thought to be typical of spring. According to solar term, spring begins on February 4 and ends on May 4. Calendars typically give the first, but the second and third are more in line with common use.In the southern hemisphere, the meteorological definition is from September 1 through November 30, corresponding to the fall months in the north.