<p>Conservation agriculture (CA) is seen as a key strategy for improving the sustainability of agriculture while being resilient to the climatic hazards due to climate change. Tunisia, which introduced CA since 1999, is struggling to develop this practice on a large scale due to the lack of commitment on the part of farmers, who need tangible results to adopt this tillage method. This study investigates the effects of rainfall variations on the active vegetation period and yield of durum-wheat, and the resilience of CA in the semi-arid rainfed regions of northwestern Tunisia. The analysis reveals significant rainfall variability, with fluctuations of 40% at Boulifa/Kef (middle semi-arid) and 30% at Krib/Siliana (upper semi-arid). A declining trend in rainfall, estimated at 8 mm/year in Boulifa and 6 mm/year in Krib, has been observed in recent decades, likely explained by global warming. Early-season water deficits were found to limit crop establishment; however, fields under CA demonstrated improved soil moisture retention, enabling better vegetation growth before winter temperatures drop. April, the grain-filling stage, was identified as a critical period for water stress, characterized by mean temperatures exceeding 15 °C and evapotranspiration surpassing 100 mm, i.e., more than double the total rainfall. During the study period, these conditions caused significant yield fluctuations, ranging from 2–60 q/ha in Boulifa and 6–37 q/ha in Krib. Compared to conventional farming, CA enhanced yields and reduced yield variability, particularly during rain deficit periods. In Siliana, CA was shown to give results comparable to supplementary irrigation for wheat production across the region. These findings suggest the capacity of CA to mitigate the impacts of high temperatures and irregular rainfall, offering a sustainable strategy for improving wheat resilience in semi-arid environments.</p>