Across much of the UK, recent days have brought sunshine, unusually mild temperatures and a growing sense that spring may be arriving ahead of schedule.

Many people are wondering whether this warm spell signals an early shift in the seasons, or if it simply reflects natural fluctuations in our weather patterns. This week’s deep dive explores the timing of the seasons, how climate change is influencing temperature trends, and what the coming days and weeks are likely to bring.

How we define the seasons

There are several ways to define the start of spring, and each method offers something different. Astronomical spring begins on 20 March, marked by the spring equinox. Meteorological spring begins earlier, on 1 March, using fixed three‑month blocks to simplify climate records. But these definitions do not always align perfectly with how weather feels on the ground.

To better understand the seasonal shift, researchers often look at long‑term climate data, for example, examining mean daily temperatures to determine the warmest and coldest quarters of the year. This approach provides a temperature based definition that could possibly capture the real world transition more accurately.

Historical data from the 1961–1990 period shows that the coldest quarter typically ran from 6 December to 6 March, while the warmest stretched from 12 June to 10 September. This method suggests that spring begins around 7 March, later than the meteorological start, but earlier than the astronomical one.

Seasonal changes in a warming climate

More recent climate averages (1991–2020) reveal that while the timing of the warmest and coldest quarters has changed very little, the temperatures within those quarters have risen noticeably, by around 0.8°C in both summer and winter. These increases, while seemingly modest, have a measurable effect on how long each season feels.

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When applying the colder threshold temperatures of past decades to today’s climate, winter appears significantly shorter, by as much as a month, while summer is only slightly longer. By this way of assessing the season, winter now often begins later in December and ends earlier in February because temperatures more quickly rise above the historical winter threshold. Summer, on the other hand, has steep temperature gradients either side of its peak, meaning that small increases in average temperature do not shift its start or end by much.

This helps explain why many people perceive winter as becoming milder and shorter, while warm conditions associated with spring and early autumn occur more frequently outside their traditional windows.

What recent weather tells us

Looking at this winter’s progression, temperatures began very mild in early December before dropping sharply around Christmas and into the first half of January. Since then, much of the UK has oscillated close to seasonal averages, with the northeast staying notably colder at times. However, in the past few days, temperatures have risen sharply, bringing the warmest spell since early November.

By some definitions, this year’s winter may have lasted only from Christmas Eve to roughly 22 February, a notably short period. While it may be too early to declare winter fully over, the recent rapid rise in temperatures certainly aligns with the typical onset of spring‑like conditions in a warming climate.

The role of the jet stream in the current warm spell

A key driver of this week’s mild weather has been the position and shape of the jet stream. Recently, the jet stream has dipped to the south over the Atlantic before arching back north over the UK. This pattern has allowed warm subtropical air to move across the country, lifting temperatures well above average and producing widespread sunshine across England and Wales.

This same jet‑stream pattern was influenced in part by a powerful winter storm that hit northeastern North America, injecting additional energy into the Atlantic storm track. As that system cleared out, it helped amplify the jet stream, funnelling warmth into the UK. This setup is now reaching its peak, with temperatures in parts of the southeast reaching 17–18°C, unusual for late February and comparable to early summer values in some years.

READ MORE: When does Spring start?

Cloud formations revealing atmospheric dynamics

This week, satellite imagery revealed classic “cloud streets”, rows of cumulus clouds forming parallel to the wind direction, across central England. These occur when rising warm air is capped by a temperature inversion, causing air to circulate in narrow, tubular patterns. Stronger winds help organise this convection into long, straight rows visible from space.

Meanwhile, across Wales and parts of northern England, a different pattern emerged: perpendicular rows of cloud produced by air being forced over hills and then descending on the other side, creating alternating areas of cloud and clearer skies. Phenomena like these not only make for striking satellite images, but also highlight the interplay between topography, wind direction and atmospheric stability.

Short‑term forecast: warmth peaking before change arrives

The warmest conditions of this spell are expected on Wednesday and Thursday, with temperatures highest across eastern and southeastern England. Scotland and Northern Ireland will be cloudier, with more persistent rain in the northwest, but even here temperatures remain above average.

By Thursday, a cold front arrives from the west. Although it will initially stall across central and southwestern parts of the UK, further frontal systems will begin to move through, gradually bringing cooler, more unsettled weather. Rain will become widespread at times, most frequent and heaviest in western areas, particularly western Scotland, Northern Ireland, northwest England, North Wales and parts of the southwest.

Friday looks brighter for many areas once the front clears, but showers will continue across northern regions. Through the weekend, the jet stream returns to a more typical westerly alignment, allowing a parade of low‑pressure systems to move in from the Atlantic. These will again bring spells of rain, especially across western hills, with windier conditions developing at times.

Early March outlook: a familiar mix

Forecast models suggest that early March is likely to continue the current theme: a prevailing westerly airflow bringing periods of rain and showers, particularly in western areas, with temperatures remaining above average for many. Although not as warm as this week, conditions may still feel spring‑like at times.

READ MORE: Why has it been so wet this winter?

High pressure over central Europe or Iberia may occasionally extend far enough north to bring drier interludes across southern parts of the UK. However, low pressure near Iceland remains influential, ensuring that the weather continues to oscillate between mild, breezy spells and cooler, unsettled periods. This combination, milder temperatures but frequent wind and rain, is characteristic of early meteorological spring.

So, is spring here?

While it may feel like spring has already sprung, the reality is more nuanced. Rising temperatures and increasing sunshine reflect early‑season warmth but do not guarantee lasting change. With a shift back to more unsettled conditions expected soon, the coming weeks will likely bring a blend of spring‑like days and more typical early‑March weather.

However, climate trends show that warmer conditions are becoming more common earlier in the year, shortening the coldest part of winter and making these spring‑like interludes more likely. Whether this warm spell is a fleeting break or part of a broader shift will become clearer as the season progresses.

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