Cells live in time varying environments with multiple desirable locations separated by unfavorable regions. To study cell navigation in spatiotemporally varying environments, we developed a microfluidic “race-track” device to create traveling attractant waves with multiple peaks and a tunable wave speed (υw). We found that while the population-averaged chemotaxis drift speed (υd) increases with υw for low υw, it decreases sharply for high υw. Our single cell measurements revealed that this reversed dependence of υd on υw is caused by a “barrier-crossing” phenomenon, where a cell hops backwards from one peak attractant location to the peak behind by crossing an unfavorable (barrier) region with low attractant concentrations. The barrier-crossing process is enabled by the cell’s random motion, which acts as temperature in thermally activated processes. Our simulation results and theoretical analysis showed that the backward barrier is lowered by υw and the backward drift speed depends exponentially on υw, leading to the observed sharp drop in υd for high υw. The barrier-crossing effect is further confirmed in double well experiments.