Ethiopia is a country of natural contrasts in the greater horn of Africa. Ethiopia has hitherto been prone to extreme weather events, with very high intensity and spatially and temporally explicit variability. Therefore, the objective of this paper is to analyze the variability and trends of rainfall onset, cessation, Length of Growing Season (LGS), annual and seasonal rainfall and climate indices. The user-defined method was applied to determine the onset date, cessation date, and LGS in this analysis. The non-parametric Mann-Kendall trend test was used for trend analysis in onset date, cessation date, LGS, annual and seasonal rainfall, and climate indices. The onset of the rainy season was highly variable at Asasa and Kulumsa with the CV value of 30% at both stations. The lowest variability is observed at Dinsho and Ginir with a CV value of 10%. On the other hand, the season ceased early on 11th September at Asasa and late end on 16th November at Ginir. The lowest variability of cessation date was determined at Arsi Robe with a coefficient of variation value of 1% and the highest variability at Dinsho with a 10% CV value during the study period. Overall, the onset of the rainy season was highly variable than the end of the season in the study area. The trend analysis of weather events showed that the onset of the rainy season was insignificantly increased in all stations except Dinsho and Ginir whereas the cessation date and LGS were decreased overall sites except Ginir and Kulumsa. This indicated that late-onset and early-cessation of the rainy season were experienced in the study area. The trend analysis of climate indices indicated that most of the temperature indices were changed significantly while most of the precipitation indicators showed non-significant and decreasing trends.