Observations of the strong and persistent glacier wind were made on the 40km-long San Rafael Glacier (46°41'S, 73°51'W) in the Patagonia Northern Icefield, Southern Chile, South America. From observations near the glacier terminus, glacier wind characteristics in the warm summer season were revealed to be as follows. The wind blows at a frequency of 80 to 90% during the summer season. In the strongest and also most frequent case, the thickness is more than 100m and maximum wind speed is 5m/s . The strong and persistent glacier wind is due to the large scale of this glacier. The main regulating factor for the day to day variation in the occurrence of the glacier wind is the upper air wind speed. When the upper wind is strong, the glacier wind is suppressed and the depth of the glacier wind is shallow. The factor determining the diurnal variation of this wind is the temperature of the ambient air outside the influence of the glacier. There exists a periodicity of 1 to 3 hours in the wind speed of the glacier wind on developed days. The continuance of this wind system after it leaves the glacier is limited to a short distance. Analyzing wind data on glaciers in various regions of the earth, glacier size seems to affect the surface wind speed, probably due to the existence of these glacier winds.