Spring has more than one “official” start date, depending on which system you use.

The two main “official” starts

  • Astronomical spring
    • Starts at the spring (vernal) equinox , when Earth’s axis is not tilted toward or away from the Sun and day and night are roughly equal.
* In the Northern Hemisphere this usually falls on **March 19–21** each year.

* For 2026, many sources list **March 20, 2026** as the start of spring.
  • Meteorological spring
    • Defined for climate and weather statistics as full calendar months.
* In the Northern Hemisphere, meteorological spring runs **March 1 – May 31** , so by this definition spring “officially” starts on **March 1**.

So if someone asks “when does spring officially start?”, many scientists and calendars mean the spring equinox around March 20 , but weather services often say March 1.

Other traditional definitions

Some traditions and older calendars use different markers:

  • Celtic/folk traditions in parts of Europe sometimes treat early February (around St Brigid’s Day, February 1) as the start of spring, based on older seasonal divisions and natural signs like plant and animal behavior.
  • Phenological spring is based on nature: first flowers, trees budding, animals emerging from hibernation, which can shift earlier or later depending on climate and year.

What most people mean today

In everyday modern usage:

  • “Official” in astronomy/most calendars → first day of spring = vernal equinox (≈ March 20 in recent years).
  • “Official” in meteorology/climate reports → first day of spring = March 1.

If you tell someone “spring officially starts on March 20,” you’re using the astronomical definition; if a weather office says “spring begins March 1,” that’s the meteorological one.

TL;DR:

  • Astronomical spring: starts at the spring equinox (around March 20).
  • Meteorological spring: March 1 in the Northern Hemisphere.

Information gathered from public forums or data available on the internet and portrayed here.