Previous studies have reported increased interference when a task-irrelevant acoustic warning signal preceded the target presentation in cognitive tasks. However, the alerting-congruence interaction was mostly observed for tasks measuring Flanker and Simon interferences but not for Stroop conflict. These findings led to the assumption that warning signals widen the attentional focus and facilitate the processing of irrelevant spatial characteristics. However, it is not clear whether these effects are because of the temporal information provided by the warning signal or because of their alerting effects. Based on these findings, and on the open question about the nature of the warning signal intervention on visuospatial interferences, we decided to test the impact of the warning signal on the processing of irrelevant spatial features, by using a procedure suitable for measuring both Simon and spatial Stroop interferences. We also manipulated the intensity of the warning signal to study the effect of the task-irrelevant characteristics of warning signals in visuospatial interferences. For the Simon conflict, results demonstrated an increased interference provoked by the presence (Experiment 1) and intensity (Experiment 2) of warning signals. In contrast, neither the presence nor the intensity of warning signals affected the spatial Stroop interference. Overall, these findings suggest that the impact of warning signals primarily depends on the processing of irrelevant spatial attributes and on the type of conflict (e.g., spatial stimulus-response interference in Simon vs. stimulus-stimulus interference in spatial Stroop). In general, acoustic warning signals facilitate the automatic response activation, but their modulatory effect depends on the task setting involved.