We propose a hypothesis to explain the erosive phenomenon of Martian gullies under current climatic conditions. This model is consistent with the morphology and finds support in the characteristic geographic diffusion of the gullies, which seem to avoid exposure to the sun and the hottest latitudes. We hypothesize a transient flow of spring water fed by melting permafrost which can occur only in certain latitudes and altitudes, with seasonal variability and for a very short time. Furthermore, this phenomenon can only occur in certain ranges of temperature and pressure, therefore when particular and sporadic weather conditions allow it. For this reason, we propose to call it weather-springing water (WSW).