Summer rain gave no clear repeated link to Meadow Brown flight-date spread in England and Wales in 1985-2024

We tested whether wetter summers had a wider recorded Meadow Brown flight season. We used 4,793 site-years from 159 England sites and five Wales sites in 1985-2024. A site and year model removed stable site differences. Four annual models controlled summer temperature, spring temperature and linear time. Rain slopes for flight-date standard deviation ranged from -0.05 to +0.83 days per 100 mm. All four corrected intervals included zero. First-to-last date ranges also gave no clear repeated link. Count controls and stricter record rules did not establish a common rain response. An early England estimate was sensitive to spring-temperature control. The Wales sample was small and had no eligible 2020 record. Coarse weather, selected detected populations, unknown visits and short annual series limit inference. This result does not show that rain has no effect. It does not identify a causal climate effect. The package includes source hashes, input extracts, code, all estimates and independent numerical checks.

phenology · butterflies · rainfall · observation bias · regional replication · null result