When Do Seasons Start May 2026

Trenberth, K. E. (1983). "What are the seasons?" Bulletin of the American Meteorological Society , 64(11), 1276–1282. https://doi.org/10.1175/1520-0477(1983)064<1276:WATS>2.0.CO;2

Here’s a useful and well-cited paper that directly addresses the question of when seasons start, including both astronomical and meteorological definitions, as well as phenological and climatic perspectives: when do seasons start

"Defining seasons: a quantitative approach to the onset of spring, summer, autumn, and winter" (or similar — but the classic reference below is key) Trenberth, K