When a precise definition is required—for legal, agricultural, or scientific purposes—the meteorological standard is recommended for its consistency and ease of use.

In the Northern Hemisphere, spring is typically considered to begin around March 20th or 21st, with the vernal equinox, and to end around June 20th or 21st, with the summer solstice. The months that are commonly considered to be part of the spring season are:

September, October, November, and December. Meteorological Spring (The Calendar)

The astronomical definition is based on the vernal equinox (spring equinox) and the summer solstice. This results in variable start and end dates, typically:

Meteorologists and climatologists use a simpler system. They break the year into four three-month periods based on the annual temperature cycle and the Gregorian calendar. This makes it easier to track weather statistics. March 1 to May 31. Southern Hemisphere: September 1 to November 30. Spring Around the World