Taiwan straddles the tropical and subtropical zones and has warm summers and mild winters. The climate is moderated by the warm water of the Kuroshio Current. The summer is long, lasting from April until November (200 days or more). In cold months the mean monthly temperature is about 15 Centigrade degrees. Beginning with April, the mean monthly temperature is above 20 Centigrade degrees. The highest mean monthly temperature reaches 30 Centigrade degrees from June to September. Lowland Taiwan is frost free. The temperature fall with altitude, and in winter the central mountains are covered with snow. Mean precipitation is 102 inches, although in some years the precipitation in summer along may exceed 200 inches. The upland are receives more rain than the west part. Rainfall is more even in the north. The precipitation in summer is about 80 percent of the annual total. There are more typhoons in July, August, and September than any other times; about 78 percent of the total occurs in these three months.