The record-breaking heat of 2026 resulted in Britain's second-best butterfly season of the past 16 years, according to the Big Butterfly Count. Over 100,000 volunteers counted almost 1.4 million common butterflies and day-flying moths during the five-heatwave summer.
Painted ladies, a migratory species, saw their numbers increase by 335% compared to last year, marking their second-highest count since the Big Butterfly Count began in 2010. The holly blue and gatekeeper species also recorded their best ever results in the count.
Despite the high numbers, Butterfly Conservation has issued a warning that drought conditions across many parts of Britain could lead to a collapse in butterfly populations next year. Richard Fox, head of science at Butterfly Conservation, noted that while adult butterflies thrive in hot, sunny weather, the same conditions can be detrimental to caterpillar offspring and their food plants.
Independent naturalist Matthew Oates expressed some hope that a wet winter last year and a wet week in early June before the drought might prevent a population crash in 2027. However, both Fox and Oates agreed that Britain is entering uncharted territory regarding the impact of new climatic extremes on native wildlife and flying insect populations.