<p>The Canary Islands are highly vulnerable to drought conditions due to their insular and geographically isolated nature, the climatic variability present on the islands, and their dependence on limited water resources. The research uses the Standardised Precipitation-Evapotranspiration Index (SPEI) to assess historical drought conditions and to project trends over three periods, under different emission scenarios. Data from meteorological stations were used for the analysis, which were spatially interpolated to capture variability between islands. The study incorporates 3-month SPEI and 12-month SPEI with the aim of representing short- and long-term drought conditions. The results show (1) an increase in drought conditions and water stress in the Canary Islands. Reductions in SPEI values are identified throughout the archipelago, although these decreases show different trends on each island. (2) SPEI projections for the western islands, characterised by higher altitudes and complex orography, predict a shift towards moderately dry climates. Projections predict 12-month SPEI values of − 1.4 under the SSP5-8.5 scenario by the end of the twenty-first century. The eastern islands, with lower altitudes and a more arid climate, present more worrying results, as more severe droughts are predicted. The most critical projections are expected in Fuerteventura, where 12-month SPEI values fall to − 2.2 in the SSP5-8.5. These findings highlight (3) the need to implement climate adaptation strategies specific to each region and island. Western islands should focus their efforts on measures that include ecosystem conservation and improved agricultural practices. Eastern islands will prioritize the reinforcement of water infrastructure and developing stricter management policies.</p>