Rainfall is the most important but variable climatic element in semi-arid regions. The present study assessed rainfall variability at Adwa District, central Tigray, Ethiopia. The assessed gridded climate data revealed that the long-term annual rainfall showed high variability from year to year with 22.9% coefficient of variation. Seasonally, the MAM total rainfall showed higher variability than the JJAS total rainfall amount. Hence, indicated that (seasonally) ONDJF, JJAS, MAM, and the annual total rainfall amount had been failing increasingly in the study area with 89.7%, 24.7%, 62.7% and 22.9% respectively.

Except onset date, cessation date and length of growing season were highly variable. The main/JJAS season curves of dry spell probability at different lengths Dry spell length converges to their minimum during months of peak rainfall periodsfrom180DOY-250DOY (28June-06Sep) and diverges again from 250DOY--265DOY (06Sept-21Sep)signaling end of the growing season. This suggests that standing crops after this time will face increasingly greater risk of water shortages in the study area. Except ONDJF with insignificant increasing trend, the annual, MAM, JJAS and MAM rainfall amount was decreasing significantly. The Probability of occurrence of dry spell length during the main season/JJAS in association with significant decreasing trend in rainfall amount in the main season/JJAS had a negative impact on the agricultural activities of the study area during the study period (1983-2013).