For an island placed in the Aegean Sea, Samothraki is gifted with high annual surface runoff and numerous perennial springs and streams. This is due to the mountainous heights of Samothraki that, contrary to the other Aegean islands, are commonly covered by snow during winter and spring, receive more rainfall, and have lower temperatures, and thus lower evapotranspiration rates. However, summer rainfalls are rare as the data of a mountainous meteorological station (placed by HCMR at 800 m asl) confirmed. Nevertheless, numerous small perennial headwater springs, surrounding the mountain peaks, are outflowing from restricted fractured type aquifers. These springs feed the streams radiating outwards from the central heights and are considered as the main sources of the island’s surface runoff. However, considering the low capacity of ground water aquifers, sparse summer rains alone cannot explain the existence of spring flow. We thus assume that spring runoff during summer may be triggered either by vapor condensation which is considered as a significant hydrological input in mountainous areas or by local orographic drizzles. This is further corroborated by the common presence of cloud and fog cover over high altitudes, that create water droplets during summer nights, confirmed by meteorological data showing frequent 100% night air humidity. Increased night runoff of springs and streams, as observations and data (according to an automatic level recorder placed at Fonias stream outflow) illustrate, further support this view, since vapor condensation primarily occurs during the night when temperature drops. These data confirm that vapor condensation is a quantitative phenomenon that, in combination with orographic drizzles, largely contributes to the existence of perennial springs and streams on the island. Further research is underway to quantify this phenomenon.