As noted earlier, Mongolia has a very dry climate with extreme and widely fluctuating inland, or continental, temperatures.  Humid air from the Pacific, Indian and Atlantic Oceans is blocked by large mountain chains on all sides. Mongolia has four distinct seasons with long, cold dry winters and short, warm and wet summers. Cloud over and precipitation is more pronounced in Mongolia mountainous and forested north and decreases southwards through rolling steppe and semi-desert.

With an average of 260 sunny days a year it’s hardly surprising that Mongolia is known as “The Land of the Blue Sky”. While winter temperatures in the north drop as low as -25°C (-13°F), Mongolia’s summers – when most tourists visit - are generally pleasant. Spring is most notoriously unpredictable and autumn is regarded by Mongolians as the best time of year.

For seven to eight months of the year, Mongolia’s mean temperature is actually below freezing. But in the short three mounts of summer, the weather turns warm and pleasant in most of the country but with temperatures in the Gobi Desert rising to 40°C (104°F). (Night temperatures here can still drop dramatically, however.) Winter lasts from mid-October to April, with January the coldest month averaging -26°C (-15°F). Although a high-pressure ridge over northwest Mongolia provides sunny if freezing days, snow does fall but is relatively light except on mountains peaks. Lakes and rivers are frozen solid up to a meter thick. In some regions such as the northwest, winter temperatures can drop to -50°C (-58°C). The lowest temperature ever recorded was -58° (-72.4°C) at Uvs Lake in the Great lakes region. Even in the Gobi, winter temperatures can drop to -40°C (-40°F). No wonder Mongolia’s average annual temperature is barely 1°C (33.8°F).

But the greatest disaster that Mongolian winters can bring is the zud when blizzards, fierce winds and record low temperatures combine to freeze grass in a layer of ice which prevents livestock from eating. Usually following unusually dry summers, the zud kills millions of animals and devastates the rural economy. In consecutive winters in 2000 and 2001, more than six million or one –tenth of Mongolia’s stock died, prompting massive domestic and foreign aid assistance. Some regions of Mongolia are still recovering from this tragedy.

“Spring is like a woman,” goes an old – and obviously very male- Mongolian saying. And the weather certainly is changeable, tempering the joys of the long winter’s end and the start of the growing cycle. Starting in March, the air pressure fluctuates madly and constant dust and windstorms blow (it can be difficult just to get out of a vehicle.) Even in May, cool days and freezing nights are followed by stifling heat waves. Overnight, blistering winds bring sudden lethal snowstorms- in early Junes 2008 one such storm killed over 50 herders and thousands of animals on their first post-winter feeding forays on Mongolia’s eastern steppe. But as the snow melts river rise, trees sprout and grass reappears, spring is needed a pleasant time.

By mid-July, Mongolia is in full summer mode. The rains begin. The entire countryside is rightly green and dotted with wildflowers. Rivers flow and waterfalls run, crops are growing and animals fattening. This is also a time of celebration, especially the naadam where everyone completes in the “three manly sports” of horse raising, archery and wrestling. In the mountainous Hangai, daytime temperatures rise to 20°C (68°F) while out on the steppe are comfortable highs of 25°C (77°F). Without any shade, the Gobi’s 40°C (104°F) challenges visitors but the heat is dry, not humid (remember to keep up your liquid intake). But the warmth of summer also brings out Mongolia’s notorious and pesky flies, especially in its wetter regions and around desert oases (bring “industrial strength” insect repellent).

Mongolia’s highest summer rainfalls are in the Hentii , Hovsgol and Altai(up to 600mm or 24 inches) and decrease south across the steppe to the Gobi, which typically receives less than 100mm (4inches). (Ulaanbaatar averages 310mm, or 12 inches, a year). At the same time, some parts of the Gobi receive no rainfall for years and are then quite suddenly hit by raging storms and flash floods that literally change the landscape overnight. (Begun in Soviet times, Mongolia uses rock rockets to seed clouds and create more rain.)

Mongolians rave about their Golden Autumn. Temperatures and rainfall drop off, grain crops are harvested, and the grassy steppe and thick forest floors turn golden yellow (Mongolia’s larch is deciduous, turning color and carpeting the forest floors in reddish needles.)  Preparation for winter begin as herders gather fodder and move their animals to winter camps protected from the cold and wind.

Sadly, even remote Mongolia does not appear immune from the effects of global climate change. An internationally funded study in 2005 by the Assessment if Impacts and Adaptations of Climate change (AIACC), an organization that assists developing countries deal with this problem, found winter temperatures rising in Mongolia’s  high mountain regions generally drier winters and springs, and drop in annual precipitation in its central region. Summer droughts have also increased, severely aggravating the winter zud episodes in 2000 and 2001. More recent reports from the International Panel on Climate Change (IPCC) blame the phenomena for Mongolia’s   increased desertification. With world record prices for cashmere, other blame Mongolia’s skyrocketing number of goats who, unlike sheep, habitually chew grasses down to the roots.

Mongolians, especially the nomads, live totally in tune with nature and don’t rely much on scientific data. But anecdotally, visitors will certainly hear much from them about recent changes in climate (the weather is one of the first topics of conversation after formal greetings). In the spring and early summer of 2008, everyone spoke of the dry winter before and how dreadfully low the rivers and lakes were, even how slow the grass was returning.

Resource: Carl Robinson "Mongolia Nomad Empire of Eternal Blue Sky"