its climate, therefore, varies considerably. Average high temperatures in January range from in the southwest to in the far north. The presence of the Rocky Mountains also influences the climate to the southwest, which disrupts the flow of the prevailing westerly winds and causes them to drop most of their moisture on the western slopes of the mountain ranges before reaching the province, casting a rain shadow over much of Alberta. The northerly location and isolation from the weather systems of the Pacific Ocean cause Alberta to have a dry climate with little moderation from the ocean. Annual precipitation ranges from in the southeast to in the north, except in the foothills of the Rocky Mountains where total precipitation including snowfall can reach annually. Northern Alberta is mostly covered by boreal forest and has a subarctic climate. The agricultural area of southern Alberta has a semi-arid steppe climate because the annual precipitation is less than the water that evaporates or is used by plants. The southeastern corner of Alberta, part of the Palliser Triangle, experiences greater summer heat and lower rainfall than the rest of the province, and as a result, suffers frequent crop yield problems and occasional severe droughts. Western Alberta is protected by the mountains and enjoys the mild temperatures brought by winter Chinook winds. Central and parts of northwestern Alberta in the Peace River region are largely aspen parkland, a biome transitional between prairie to the south and boreal forest to the north. Alberta has a humid continental climate with warm summers and cold winters. The province is open to cold Arctic weather systems from the north, which often produce cold winter conditions. As the fronts between the air masses shift north and south across Alberta, the temperature can change rapidly. Arctic air masses in the winter produce extreme minimum temperatures varying from in northern Alberta to in southern Alberta, although temperatures at these extremes are rare. In the summer, continental air masses have produced record maximum temperatures from in the mountains to over in southeastern Alberta. Alberta is a sunny province. Annual bright sunshine totals range between 1,900 up to just under 2,600 hours per year. Northern Alberta gets about 18 hours of daylight in the summer. The average daytime temperatures range from around in the Rocky Mountain valleys and far north, up to around in the dry prairie of the southeast. The northern and western