It stretches more than 10000 km (6200 miles) north-south and more than. It takes a full week to cross by train from. A severe continental climate dominates nearly half of the russian federation, with long cold winters and relatively short warm summers. Permafrost occurs in more than 2/3 of the russian. In the extreme northeast, winter conditions can last for 10 months of the year. Drought is a frequent problem in the southwestern and southern parts of the russian federation. In central asia, aridity is a severe problem. The climate in this sub region is harsh: total annual precipitation in the deserts is less than 18 cm (7 inches), shade temperatures can reach 50 c (122 f) and ground surfaces can heat up to 80 c (176 f). The heat is intensified by strong drying winds that blow on more than half the days of summer, often causing dust storms.