In the Northern Hemisphere (including North America, Europe, and most of Asia), spring generally occurs during the first half of the year. Definition Start Month Typical Dates March May March 1 – May 31 Astronomical March June March 20/21 – June 20/21 Monthly Highlights (Northern Hemisphere)

The most common distinction is between astronomical spring and meteorological spring. Astronomically, spring is defined by the Earth’s position relative to the Sun. In the Northern Hemisphere, spring begins with the vernal equinox, which occurs around March 20 or 21, when day and night are approximately equal in length. It ends with the summer solstice around June 20 or 21, the longest day of the year. Thus, according to the astronomical calendar, spring includes the latter half of March, all of April and May, and the first part of June. In the Southern Hemisphere, the seasons are reversed: astronomical spring runs from September 22 or 23 to December 21 or 22, encompassing parts of September, all of October and November, and part of December.

This definition is based on the annual temperature cycle and the Gregorian calendar. For the sake of consistent data and statistical comparisons, meteorologists divide the year into four three-month blocks.