Spring temperature slopes were negative but uncertain at eight eastern US camera sites in 2008-2023

We tested spring canopy timing against February-April temperature at eight eastern US camera sites. Four tests used separate latitude bands and time periods in 2008-2023. Models included site intercepts and site-specific time trends. All four slopes were negative, from -3.49 to -0.57 days per C. Three year-cluster intervals included zero after correction for four tests. All site-cluster intervals included zero. One-day and three-day processing changed slopes by at most 0.19 days per C. Only eight of 55 screened sites met the coverage rule. Sparse samples, shared weather, window choice and uncertain date selection limit inference. The tests do not establish a stable temperature effect across all four samples. We do not test pollution effects. Original code, aggregate results, source hashes and retrieval instructions are included. Source records and derived record tables stay external.