<p>Rainfall variability in the Sahel is characterized by pronounced intra‑seasonal irregularity, with a limited subset of rainy days slightly less than half of the total accounting for most of the annual rainfall share. This study investigates how daily rainfall concentration (CI1) has evolved in the Sahel over the recent period (2000–2025) and identifies the regional contrasts that emerge. The objective is to quantify CI1 trends and to pinpoint areas of hydrological and agricultural vulnerability. The methodology combines the Mann–Kendall test (MT), Sen’s slope estimator, and innovative trend analysis (ITA), applied to multi-station datasets covering six Sahelian countries. The results reveal a significant to highly significant increase in CI1 in Burkina Faso, Niger, and Senegal, sporadic increases in Chad and southern Mali, and prevailing stagnation in Mauritania and Saharan Mali. These contrasts confirm the existence of a north–south gradient, with intensified rainfall concentration in southern areas while northern regions remain comparatively stable. Looking ahead, the study underscores the need to deepen the analysis of concentration indices, explore their links with climate teleconnections (ITCZ, AEJ, NAO, WeMO), and integrate CI1 as an operational indicator in water resource adaptation and management policies across the Sahel.</p>