The Valira d'Orient is the northeast tributary, flowing from near Grau Roig through Soldeu, Canillo, Encamp, and Les Escaldes where it meets the Madriu River and then the Valira del Nord, becoming the Gran Valira. There are also several much smaller drainage basins that span Andorra's borders with France and Spain. The most notable of these is the Pic de Maià basin whose main river, the Sant Josep, flows easterly out of the country into France and is a tributary of the Ariège River. Andorra has 172 lakes, of which the largest is Estanys de Juclar () near Pic de Noé in the north east. The climate in Andorra varies greatly with elevation. The valleys have a climate that is similar to the temperate climate of Andorra's neighbours, but because of the higher elevation, winters tend to be more severe, the humidity lower, and summers slightly cooler. Regions above the Alpine tree line at about have an alpine climate and alpine tundra. Snow completely covers the northern valleys for several months. There are, on average, 300 days per year of sunshine. Average daily peak insolation varies from 1150 W/m2 in June to 280 W/m2 in December. The average annual temperature varies from in Sant Julià de Lòria in the south, to in La Massana in the centre, and to in Arcalis in the north. The average daily high and low temperatures in Escaldes-Engordany are, respectively, and in July, and and in January. Average annual precipitation is for the whole country, but it varies across the country, increasing with elevation and from south to north. The driest parish is Sant Julià de Lòria ( per year) in the south, and the wettest is Canillo ( per year) in the north. Annual precipitation can exceed the highest mountainous areas. The driest months tend to be January and February, and the wettest, May, June, and November. During the summer months, there are very few rainy days, but the rainfall can be very heavy because it is associated with thunderstorms. Deposits of iron ore, lead, alum, and building stones are among the resources exploited in Andorra, although the economy depends to a much greater extent on tourism. Andorra's mountainous terrain attracts about 13 million tourists annually, primarily for skiing and hiking.