Mongolia’s climate is very dry with extreme continental temperatures. Humid air from the Atlantic and Pacific Oceans are blocked by the huge Central Asian mountain ranges. Although Mongolian winters are long and famously cold, with temperatures dropping as low as-50 degrees centigrade in the far north of the country, summers are generally pleasant. (See Table 1).
The mean temperature falls below freezing for seven to eight months of the year. For two or three months in summer, the weather is warm and pleasant and relatively hot in the southern Gobi region, where mid-summer temperatures peak at around 40 degrees and there is little shade available.
Winter usually lasts from mid-October until April, with the coldest period being between mid-December and the end of February or mid-March when the temperature drops to -20 or -30?C and occasionally even lower. Snow usually falls between mid-October and mid-April. There are some regions, especially in the northwest, where the temperature goes down to -40 to -50?C. In the Gobi it drops to -40C.
Spring, which generally starts in March, is known for its constant dust storms and huge fluctuations in air pressure. The steppe gradually starts to sprout fresh, green pasture and even in the capital, the change is both visible and welcome.
Summer evenings in the Western Altai range tend to be cooler and local nomads have to wear warm and heavy clothes.
The annual rain fall begins in late July and continues until September. Humidity is generally low (47-73%), especially in winter. But in the country the number of sunny days ranges between 220 and 260 a year.
More Info: Climate Ulaanbaatar