When does spring start in the UK? Meteorological vs astronomical definitions explained

Why the start of spring can be confusing

Spring is widely seen as one of the most anticipated parts of the year: a move away from the darker, colder months into a season that feels brighter, lighter and associated with renewal. Yet the seemingly simple question “when does spring start?” does not have a single, universal answer.

In the UK, spring can begin on different dates depending on which definition you use. Two approaches are commonly used: the meteorological calendar and the astronomical calendar. Both are widely recognised, and each offers a useful way to describe seasonal change—whether your focus is on consistent climate records or on the Earth’s position relative to the Sun.

Understanding these definitions is not just a matter of curiosity. A clear way of marking spring supports the recording and communication of seasonal shifts that influence patterns such as temperature changes and pollen levels. And beyond science, spring carries cultural and emotional meaning for many people, linked with new life, blossoming plants and the gradual return of warmth.

Meteorological spring: a fixed, practical season

Meteorological seasons divide the year into four fixed blocks of three months each. This approach is designed to be simple and consistent, which makes it especially useful when comparing long-term records and identifying broader patterns in climate data.

In the UK, meteorological spring always runs from 1 March to 31 May. Because the dates never change, scientists and forecasters can more easily analyse and compare year-to-year variations in temperature, rainfall and sunshine within the same seasonal window. That consistency supports climate monitoring, long-term forecasting and communication about typical seasonal conditions.

Under this framework, spring is often described as a bridge between winter and summer. Day-to-day weather can still vary sharply, but the season provides a structure for tracking the overall shift from cooler, more unsettled winter conditions toward warmer weather later in the year.

Astronomical spring: linked to the Sun and the equinox

Astronomical spring is defined by the Earth’s position in relation to the Sun rather than by fixed calendar months. It begins at the vernal equinox, which occurs around 20 March in the Northern Hemisphere.

On the equinox, day and night are roughly equal in length. It marks a turning point in the year, after which daylight hours begin to increase more rapidly. For many people, this idea of a “balance point” between darkness and light fits closely with how spring feels—brighter mornings, longer evenings and a clear sense that the year is opening up.

Unlike meteorological spring, the exact date of the vernal equinox can vary slightly from year to year. This is explained by the Earth’s axial tilt and the slightly elliptical shape of its orbit around the Sun. Even with small shifts in timing, the astronomical definition remains closely tied to natural cues that many associate with spring’s arrival.

Two definitions, two purposes

It can be tempting to treat one definition as “correct” and the other as secondary, but they serve different purposes.

• Meteorological spring is fixed and consistent, supporting clear comparisons of seasonal climate statistics and easier communication about weather patterns.
• Astronomical spring is anchored to the Earth–Sun relationship and the equinox, reflecting the natural turning point when daylight begins to dominate more strongly.

In practice, you may hear both used in forecasts and seasonal discussions. The key is to understand which definition is being referenced and why.

How people often notice spring before any “official” start

Calendars and equinoxes provide useful scientific markers, but many people experience spring as a gradual transition rather than a date. In the UK, signs of spring are often noticed well before either 1 March or the vernal equinox, because nature responds to changing light and temperature in ways that are visible and familiar.

Longer daylight: one of the clearest signals

One of the most recognisable changes is the steady increase in daylight. After the vernal equinox, the balance tips toward longer days, with earlier sunrises and later sunsets. This shift is more than a pleasant feature of the season: increasing daylight plays a major role in shaping the behaviour of plants and animals and can also influence people’s sense of energy and wellbeing.

Even before the equinox, many notice the lengthening afternoons and the way brighter evenings begin to change daily routines. The sense of “more day” is one reason spring can feel like a fresh start, regardless of what the calendar says.

Rising temperatures, with chilly nights still possible

As the Sun climbs higher in the sky during spring, daytime temperatures begin to rise. In many parts of the UK, warmer afternoons become increasingly common, particularly toward late April and May.

However, spring warmth is not always consistent. Nights can still feel cold, partly because the ocean remains relatively cool after winter. This contrast—mild afternoons followed by chilly evenings—helps explain why spring clothing can be tricky: the season often demands flexibility.

Plants and wildlife: the seasonal story in motion

For many, the most vivid signs of spring come from the natural world. Blossoming trees, the return of birdsong and increased insect activity are classic indicators that spring is underway.

These changes are part of what scientists call phenology, the study of seasonal changes in plants and animals. Phenology connects the timing of natural events—such as flowering or increased wildlife activity—to shifting environmental conditions through the year.

Even the language of spring reflects this association with growth. The word “vernal,” used in “vernal equinox,” comes from Latin for “bloom,” echoing the burst of colour and life that many people associate with the season.

Spring weather in the UK: varied and sometimes surprising

Spring is often imagined as steadily warming and increasingly settled. In reality, it can be one of the most changeable seasons. The atmosphere is adjusting from winter toward summer, and that transition can bring a mix of calm, dry spells and sudden shifts in conditions.

This variability is part of what makes spring weather so memorable. A bright, mild day can be followed by a sharper, colder spell, and the overall pattern can feel like a tug-of-war between lingering winter influences and the growing strength of the spring Sun.

Spring doesn’t arrive everywhere at the same pace

Another reason spring can feel hard to pin down is that it does not arrive uniformly across the UK. Regional differences shape how the season is experienced.

Northern areas, including Scotland, typically stay cooler for longer, while southern parts of the UK tend to warm earlier. These contrasts can be seen in the timing of early blooms, the persistence of colder nights, and the overall pace at which spring-like conditions become established.

As a result, the “start of spring” can feel earlier in some places and later in others, even when everyone is using the same definition on paper.

Can it still snow in spring?

Despite spring’s reputation for milder weather, snow remains possible—especially in March. Statistically, March has a higher likelihood of snow or sleet than December in the UK.

This is one of the reasons late cold snaps can feel so surprising: many people mentally move on from winter once the calendar turns, but the climate does not always follow that expectation. Snow around Easter may seem unusual, yet it is not out of place in the UK’s typical seasonal pattern.

What long-term averages say about UK spring temperatures

Long-term climate averages help describe what spring is typically like across the UK, even though individual days and weeks can deviate significantly.

Across the 1991–2020 climate period, the long-term average UK spring temperature is 8.08°C. This reflects the overall warming trend through March, April and May, with May typically bringing the first consistently warm days of the year.

For comparison, the long-term average UK winter temperature is 4.09°C, highlighting how spring represents a notable shift upward in average conditions as the year progresses.

Why seasons change at all: the role of Earth’s tilt

Whether you mark spring by fixed months or by the equinox, both sit within a larger explanation of how seasons work. The cycle of seasons is shaped by the Earth’s tilt.

The Earth’s axis is tilted at 23.5 degrees. As the planet orbits the Sun, different regions receive varying amounts of solar radiation at different times of year. This changing sunlight is what produces longer days and rising temperatures in spring, followed by the warmth of summer, the cooling of autumn, and the shorter days of winter.

Understanding this process helps explain not only when spring begins, but why it matters: the seasonal shift in light and temperature influences weather patterns and the natural rhythms of plants and animals.

So, when does spring start?

The answer depends on which definition you are using:

• Meteorological spring in the UK starts on 1 March and ends on 31 May.
• Astronomical spring begins at the vernal equinox, around 20 March, with the exact date varying slightly each year.

In everyday life, many people also judge spring by what they can see and feel: longer daylight, rising daytime temperatures, and the return of blossoms and wildlife activity. Taken together, these perspectives show that spring is both a date on a calendar and a gradual transition that unfolds across the UK in different ways.

A season defined by change

Spring’s appeal lies partly in its sense of momentum. It is a season of increasing light, shifting temperatures and visible change in the natural world. It can also be a season of contrasts: mild afternoons and cold nights, calm spells and sudden changes, early warmth in the south and lingering chill further north.

That complexity is why the start of spring can be described in more than one way—and why both the meteorological and astronomical views remain useful for understanding what is happening in the atmosphere and in the landscape as the year turns toward summer.