Changes and variability in rainfall onset, cessation, and length of rainy season in the IGAD region of Eastern Africa

Abstract Rainfall onset dates (ROD), rainfall cessation (RCD) and length of rainy season (LRS) are crucial for crop production food security in Eastern Africa yet scantily documented. This paper seeks to investigate the spatial patterns these parameters. Data used Climate Hazards Group InfraRed Precipitation with Station data (CHIRPS v2.0) National Oceanic Atmospheric Administration (NOAA) gridded temperature. Threshold 1 mm day, 20 over 5 days at least 3 rain dry spell not exceeding 7 next 21 were determine RODs. The Potential Evapotranspiration (PET) Water Balance (WB) criteria computed RCDs. differences between ROD RCD calculating LRS. results showed early more than 30 counties Kenya lead shortened by 10–20 during MAM season. Similarly, 20–40 observed most upper Nile, Unity, Jonglei states South Sudan, while delayed was Khartoum southern parts Nile state western Darfur, eastern Aljazeera Ethiopia Eritrea districts JJA Highlands Nyanza region Kenya, Uganda March no sign before November. Early northern behind LRS, furthermore, RODs southwestern increased Prolonged conditions southeastern central Somalia, Darfour, Kordofan Sudan exacerbated significant rainfall. These findings important rain-fed agricultural planning IGAD Africa.