Climate change has significantly influenced the characteristics of seasons and negatively affected ecosystems and socio-economic life. This study presents a new, objective definition for seasons in the Arabian Peninsula. Specifically, the study determines disruptions in the onset, cessation, and duration of winter, spring, summer, and autumn based on mean intra-annual changes of 12 climatological parameters from 1950 to 2019. Data for climatological parameters were obtained from the National Centers for Environmental Prediction (NCEP)/National Center for Atmospheric Research (NCAR) reanalysis. These data were analyzed using two multivariate statistical methods: principal component analysis and cluster analysis. The results show that the characteristics of the four seasons differ from conventionally defined seasons. The differing characteristics of the four seasons are (a) that winter extends for 91 days, between 2 November (the previous year) and 31 January; (b) spring extends for 111 days, until 22 May; (c) summer extends for 106 days, until 5 September and, finally; (d) autumn completes the cycle, extending for 57 days. To investigate the decadal disruption of seasons' characteristics, the analysis was performed on the data collected during five overlapping 30-year periods: 1950– 1979, 1960–1989, 1970–1999, 1980–2009, and 1990–2019. The most remarkable changes were noticed during the last 30 years. Compared to the 70-year analysis, the 1990–2019 analysis showed extra prolongation in the duration of summer and a shortage in winter, which aligns with the recent warming and drying of the Arabian Peninsula. Summer (winter) lasts for 126 (76) days. All analyses propose that all seasons start earlier, compared with the astronomical definition. The findings of this study are key to understanding the consequences of seasons changes in the Arabian Peninsula. These consequences include impacts on agriculture, water deficits, ecosystems, and land cover.