When Does Spring Arrive?

By this time of year, most of us in the UK are counting down until the Vernal Equinox on the 20th March to welcome the arrival of spring. But did you know there are actually three different definitions of spring according to astronomy, meteorology and phenology?

Astronomical spring

Astronomically, the seasons change due to the slight tilt of Earth on its axis as it travels around the sun, providing different amounts of daylight to different areas of the planet at different times of the year. Equinoxes occurs twice in a year, when the length of the day and night are equal. Mid-way between these are the solstices, when the Sun is at its highest and lowest in the sky at mid-day.

In the UK,

  • Spring is considered to begin at the Vernal Equinox (near 20th March)
  • Summer at the Summer Solstice (near 21st June)
  • Autumn at the Autumn Equinox (near 23rd September)
  • Winter at the Winter Solstice (near 22nd December)

Meteorological spring

Meteorologists divide seasons into periods of three whole months based on average monthly temperatures, with summer as the warmest and winter as the coldest. In the UK, the spring months are classed as March, April and May, meaning by this definition spring starts on the 1st March.

Phenological spring

Also referred to as nature’s calendar, phenology is the study of seasonal biological phenomena. Events such as the date of the emergence of leaves and flowers, the appearance of migratory birds, or the laying of eggs can be highly sensitive to variations in conditions such as temperature or rainfall. As one of the first flowers to bloom in the calendar year, snowdrops herald the very beginning of spring in nature’s calendar.

So, whether you decide spring starts at the start of March, when the Vernal Equinox occurs, or when the flowers start to bloom, what is certain is after a wet and windy winter, spring will make a very welcome return to many.

Don’t forget the clocks go forward by 1 hour at 1am on the 31st March.