Has climate change changed the UK's seasons?
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You don’t need to be a climate scientist to know that something fundamental is shifting in the UK's seasons.
Our calendars may look the same but the biological or phenological seasons - the ones defined by the timing of leaf burst, pollinator activity, plant flowering, bird migration and so on - are changing fast. It’s all being driven by rising global temperatures, giving us hotter summers, earlier springs and milder winters with more violent, unpredictable winter storms.
That’s why we’ve been generating green electricity for 30 years at our wind and sun parks around Britain, as we seek to end the use of fossil fuels in the energy sector.
Are summers getting longer?
Summers in the Northern Hemisphere have been stretching out for decades. A study shows that summers grew around 17 days longer between the 1950s and 2011 – and that’s not even including the latest 15 heatwave-filled years.
All the UK's top five warmest summers on record have occurred since 2000, with recent years bringing widespread heatwaves and record-breaking temperatures exceeding 40°C.
Heatwaves also expose the weakness of fossil fuel infrastructure. Gas-fired power stations lose up to 1.5% of their efficiency for every 1°C rise in temperature, resulting in efficiency losses as high as 22% during severe heatwaves. In contrast, solar generation typically performs strongly during sunny summer periods, showing that renewable energy is more resilient to our warming climate.
For agriculture, a longer growing season can bring opportunities for bumper harvests, allowing crops such as wheat and maize to be grown over extended periods. However, extended warmth can also mean droughts and parched soils - and some traditional crop varieties are struggling to cope with rising baseline temperatures.
Is autumn arriving later?
As summer grows, the other seasons shrink. Warmer autumn temperatures are delaying the classic sign of autumn – when trees shed their leaves. According to Met Office analysis, every 1°C increase in October temperature delays the date trees shed all their leaves by two to three days.
Don’t think autumn has come early if you see trees losing their leaves in late August. This is a phenomenon called ‘false autumn’ that we’ve been seeing more of recently – during droughts and heatwaves, stressed trees can drop their leaves prematurely to conserve water. It might look like autumn, but it’s actually a sign of severe environmental stress.
Warmer winters and earlier springs
The Met Office predicts that by 2070, compared to 1990, winters will be between 1 and 4.5°C warmer – and up to 30 per cent wetter. That’s because warmer air holds more water, which is why climate change is making our winters both warmer and wetter.
Recent winters have brought us record rainfall and destructive storms like Eunice and Arwen. Intense downpours have become more common in general, increasing the risk of flash flooding.
Winters are shorter, though, and spring is arriving earlier - key biological events are now occurring nine days earlier than a quarter of a century ago.
Studies show hazel trees flowering nearly ten days earlier than historical averages, while frogspawn in 2024 was recorded 17 days ahead of its average date. A Met Office analysis shows that for every 1°C temperature increase in the months leading up to spring, spring events advance by one to seven days.
The problem with this shift is that it can create a widening ‘phenological mismatch’, where events that should be in sync become disconnected. For example, early mild spells may trick animals into breeding early, leaving their young more vulnerable to late spring frosts. Plants such as apple trees may risk blossoming before their wild pollinators emerge, threatening fruit production and disrupting interconnected food chains.
You can download a fascinating phenology calendar from The Woodland Trust to track spring events - and add your own recordings of natural events to an archive that stretches back to 1736.
What will happen in the future?
Scientists agree that the UK’s weather is becoming wetter and warmer. That means the trends we’re already seeing will continue.
It doesn’t mean that every summer will be filled with heatwaves or every winter will bring record-breaking storms, but it increases their likelihood. On average, we’ll get longer, hotter summers; later autumns; milder and wilder winters; and earlier springs.
To protect our seasons and wildlife, we urgently need to cut carbon emissions and transition to clean, renewable energy.
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