In Mongolia, the climate is strongly continental, with long, frigid winters and short, warm summers: the temperature range between winter and summer is definitely wide.
Precipitation is scarce and is concentrated in summer, when the country is partly affected by the Asian monsoon; in winter, when a thermal high pressure system dominates, the sky is often clear. Precipitation is more abundant in the north, where it exceeds 300 millimeters (12 inches) per year, while in the south, which is desert, it drops below 200 mm (8 in) per year. During winter, snowfalls are frequent but usually light, in fact, they often create a thin white veil, which can be carried away by the wind. Sometimes, a light snow can even fall when the sky is clear, in fact, when the temperature is very cold, moisture can directly condense.
Much of Mongolia is occupied by a plateau at an altitude between 1,000 and 1,500 meters (3,300 and 4,900 feet), which tempers the summer temperatures. In the plateau, strong winds can blow, especially in spring. Owing to the aridity of the climate, these winds can bring dust storms, which are more frequent in the south (where they occur more than 30 days per year), quite frequent in the center (15 to 30 days per year), and very rare in the north (even less than 10 days per year). In winter, the wind associated with outbreaks of cold air masses can amplify the feeling of cold and lead to rapid frostbite to the persons who are not sufficiently covered. For example, with a temperature of -20 °C (-4 °F), which is normal in Mongolia during the cold season, a wind of 72 kph (45 mph) generates a wind chill (equivalent temperature) of -35 °C (-31 °F), and therefore the risk of freezing. When the temperature plunges below -30 °C (-22 °F), in case of prolonged exposure, there's a risk of frostbite even with no wind.
The climate in Mongolia is unstable, so, from year to year, there may be significant variations in temperature and precipitation.
The average temperature in January ranges from around -32 °C (-26 °F) in the coldest areas of the north to around -15 °C (5 °F) in the south. The temperature does not necessarily decrease with altitude, on the contrary, owing to the phenomenon of the temperature inversion, it can even increase with altitude. In fact, the coldest areas of the country are the valleys between the mountains of the north, at least in winter. On the contrary, the temperature in summer is higher in the south and at low altitude. At 1,500 meters (5,000 feet) above sea level, the daily average in July is around 13 °C (55.5 °F) in the far north, around 15 °C (59 °F) in the center-north, and 20 °C (68 °F) in the south. At 1,000 meters (3,300 feet), the daily average ranges from 16 °C (61 °F) in the north to 23 °C (73 °F) in the south. So, only at the lowest altitudes and in the south, the summer can be considered hot. The areas located at low altitudes, around a thousand meters or less, are not very large, so the summer nights in most of Mongolia are generally cool (sometimes even cold) and the days are pleasant. However, in the whole country, heat waves with peaks of 35/37 °C (95/99 °F) can occur, at least below 1,500 meters (5,000 feet).
The northern part of Mongolia lies in the permafrost area (the southern limit is more or less at the latitude of the capital), where the ground, below a certain depth, remains frozen throughout the year, and makes it difficult to build houses and infrastructures as well as to dig for extraction of raw materials.
In addition to the plateau, in Mongolia, there are mountain ranges: in the west, we find the Altay Mountains, whose highest point is Hüiten Peak, 4,374 meters (14,350 feet) high; in the west-central, we find the Khangai Mountains, which reach 4,000 meters (13,000 ft); while north of the capital, we find the aforementioned Khentii Mountains, which reach 2,800 meters (9,200 ft). The mountainous areas are those that receive the most abundant rainfall, and they are practically the only ones where you can find forests. Above 3,500 meters (11,500 ft), there are glaciers and snowfields, while at altitudes a bit lower, above 2,000 meters (6,500 feet), it can sometimes snow even in summer.
The Gobi Desert is located in the south, and although it is drier than the north, it receives some rain showers in summer, able to feed some grass as well as the camels, at least in the eastern part, where from 150 to 200 mm (6 to 8 in) of rain fall per year. The most arid area is the south-west, where precipitation drops below 100 mm (4 in) per year, and in some cases even below 50 mm (2 in).
Here is the average precipitation of Sainshand, located in the south-east, at 950 meters (3,100 ft) above sea level.
The best time to visit Mongolia is the summer, from June to August, when the temperature remains above freezing even at night, at least in the plateau and in the mountains at low altitude. Summer is certainly the rainiest period of the year, and it can be hot during the day, especially in the center and south and at lower altitudes, but at least, you avoid the bitter cold. However, in summer, it can even get cold at night, so you have to be ready to cover and uncover, depending on hour and weather conditions, in addition, it is advisable to bring a scarf, for wind and dust protection.
What to pack
In winter, it is necessary to bring clothes for the great cold, such as synthetic, thermal and long underwear, a fleece, a parka, a wind jacket, a hat, gloves, and warm boots.
In summer, bring spring/autumn clothes, T-shirts for hot days, but also a long jacket for the wind, a sweater or sweatshirt for the evening and at high altitudes, a raincoat or umbrella, a scarf for the wind-borne dust, hiking shoes, sunscreen, and sunglasses. For high mountains, a down jacket, a hat, gloves, and a scarf. A sleeping bag and a warm jacket for outdoor overnight stays.