Britain Records Second-Best Butterfly Season in 16 Years

Published: 16 September 2026. The English Chronicle Desk. The English Chronicle Online.

Britain has experienced one of its strongest butterfly seasons in recent years, with record-breaking heat and prolonged periods of sunshine helping adult butterflies flourish across much of the country. The 2026 Big Butterfly Count recorded almost 1.4 million butterflies and day-flying moths, making the season the second-best recorded in the 16-year history of the national survey.

The results provide an encouraging snapshot of Britain’s flying insects after a summer marked by five heatwaves. More than 100,000 volunteers took part in the annual survey, making it one of the largest insect-monitoring initiatives of its kind. Their observations showed particularly strong numbers for several species, including the painted lady, holly blue and gatekeeper.

Yet conservation experts have warned that the impressive figures should not be interpreted as evidence that Britain’s butterfly populations are necessarily becoming healthier. The same hot and exceptionally dry conditions that created favourable circumstances for adult butterflies may have damaged caterpillars and the plants they depend on, potentially creating serious consequences for next year.

The Big Butterfly Count showed that painted lady numbers increased by 335% compared with the previous year. The migratory species travels to Britain each summer through several generations, beginning its journey from sub-Saharan Africa. This year’s count recorded its second-highest result since the survey began in 2010.

The holly blue and gatekeeper also produced their strongest results since the survey began, while the small copper recorded its third-best season. Overall butterfly numbers were the strongest recorded since the summer of 2019, highlighting the exceptional conditions experienced by many adult butterflies during the warm months.

For people spending time outdoors, the increase was highly visible. Gardens, grasslands and other areas with flowering plants provided feeding and breeding opportunities, while warm, sunny weather encouraged butterflies to remain active for longer periods. The abundance of colourful insects became one of the more noticeable features of the unusually hot summer.

However, Butterfly Conservation has stressed that adult butterfly numbers provide only part of the picture. Richard Fox, the organisation’s head of science, said hot and sunny conditions are beneficial for adult butterflies because they support flying, feeding and breeding. But he warned that population health depends heavily on what happens to caterpillars and the plants on which they rely.

The prolonged drought across many parts of Britain caused grasses, wildflowers and other vegetation to become severely dry or die back. Caterpillars developing during the summer could therefore have faced shortages of food and suitable habitat. Since many of those caterpillars would normally develop into adult butterflies during the following year, their survival could have a significant influence on future numbers.

The contrast between this year’s adult butterfly abundance and the potential risks facing future populations illustrates the complexity of climate effects on wildlife. Warm weather can provide immediate advantages for insects that depend on sunshine and higher temperatures, while prolonged drought can create damaging conditions for their food plants.

Britain has experienced similar patterns before. Following particularly successful butterfly seasons in 1976 and 1995, populations subsequently suffered major declines, with drought identified as an important contributing factor. However, conservation experts caution against assuming that every drought will produce the same outcome.

More recent periods of severe dryness, including the droughts of 2018 and 2022, did not lead to comparable population collapses. Differences in rainfall before and during the summer, local conditions and the resilience of individual plant species can all influence how wildlife responds to extreme weather.

Independent naturalist Matthew Oates, who has recorded butterfly seasons for decades, said the circumstances surrounding the 2026 drought differed from those preceding the severe conditions of 1976. The year before this summer was relatively wet, while rainfall early in June also provided some moisture before the drought became established.

Oates has spent many years observing butterfly populations and maintaining detailed records of seasonal conditions. His observations in parts of the Cotswolds and Wiltshire found that some important grassland plants had survived better than might have been expected, although plants growing on south-facing slopes appeared more vulnerable to the extreme heat and dryness.

Among the plants important to grassland butterflies is horseshoe vetch, which supports several species during their development. The survival of such food plants could prove important if rainfall returns and vegetation recovers before the next breeding cycle.

The outlook is therefore uncertain. A wet winter or favourable spring could help restore vegetation and improve conditions for caterpillars. Conversely, another period of extreme heat or drought could intensify the pressure on already vulnerable species.

Not all butterflies benefited equally from the summer weather. Some drought-sensitive species recorded relatively poor results in the latest Big Butterfly Count. Speckled wood, green-veined white and ringlet butterflies were all observed in below-average numbers.

The long-term figures for those species are also concerning. Compared with their results in 2011, the latest counts show declines of 44% for speckled wood, 54% for green-veined white and 39% for ringlet. These differences demonstrate that the effects of changing weather patterns are not uniform across Britain’s butterfly species.

Migratory butterflies, meanwhile, appear to have benefited from the warmer conditions. The clouded yellow remained active across southern Britain in September, while unusually large numbers of the non-native Queen of Spain fritillary were reported near coastal areas.

Such observations illustrate the changing ecological conditions facing Britain’s insects. Species with different life cycles, food requirements and migration patterns can respond in very different ways to the same weather conditions.

For conservationists, the key concern is whether increasingly frequent extreme weather events could disrupt those ecological relationships over time. Butterflies depend on particular plants at different stages of their development, meaning that a disruption to vegetation can have consequences that may not become visible until the following season.

Richard Fox said that very few butterfly species are likely to thrive under the type of widespread drought experienced across much of the UK this summer. His comments reflect a broader concern about how native wildlife will respond if extreme heat and prolonged dryness become increasingly common.

Oates similarly described the conditions as unlike anything he had experienced during the 62 summers for which he has kept weather and butterfly records. His long-term observations provide a historical perspective on how unusual the latest combination of heat and drought has been.

The challenge for scientists and conservation organisations is now to determine whether the strong adult butterfly season represents a temporary benefit or the beginning of a more complicated shift in populations. Monitoring over the next year will be particularly important because the effects of this summer’s drought may become clearer as caterpillars develop and emerge.

The results also underline the value of large-scale citizen science. With more than 100,000 volunteers participating, the Big Butterfly Count provides conservation researchers with a substantial body of observations collected from locations across Britain. Such records help scientists identify changes between years and track which species are increasing or declining.

For the public, the season has offered an unusually vivid reminder of Britain’s insect life. The sight of large numbers of butterflies during a hot summer may appear to signal favourable conditions, but the underlying ecological picture is more complicated. A thriving population requires suitable plants, adequate moisture and safe conditions throughout the entire life cycle.

Britain’s second-best butterfly season in 16 years has therefore brought both celebration and caution. The exceptional numbers of adult butterflies recorded in 2026 demonstrate how strongly insects can respond to warm, sunny conditions. At the same time, the drought has raised questions about whether those immediate gains can be sustained.

As Britain faces the possibility of more frequent climatic extremes, the coming seasons will provide important evidence of how butterflies and other flying insects adapt. The latest count offers valuable data, but it also highlights a central lesson of wildlife monitoring: a strong season for adult insects does not necessarily mean that the wider population is secure.