In Mongolia the climate is strongly continental, with long and frigid winters, and short and 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, sky is often clear. Precipitation is more abundant in the north, where it exceeds 300 millimetres (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, so that they create a thin white veil, which can be carried away by the wind; sometimes a light snow can fall even when the sky is clear: when temperatures are very cold, moisture can condense directly.

Much of Mongolia is occupied by a plateau at an altitude between 1,000 and 1,500 metres (3,300 and 4,900 feet), which tempers the summer temperatures. In the plateau, strong winds can blow, especially in spring. Due 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 centre (15 to 30 days per year) and very rare in the north (even less than 10 days). In winter, the wind brought by outbreaks of cold air masses, can amplify the feeling of cold and lead to rapid frostbite to those who are not properly covered: for example, with a temperature of -20 °C (-4 °F), which is normal in Mongolia during the cold months, 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 freezing even in the absence of 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 goes from -32 °C (-26 °F) in the coldest areas of the north, to -15 °C (5 °F) in the south. The temperature does not necessarily decrease with altitude, on the contrary, for the phenomenon called temperature inversion, it may even increase with altitude: the coldest areas of the country are the valleys between the mountains of the north. On the contrary, in summer the temperature rises proceeding from north to south and going down in altitude: at 1,500 metres (5,000 feet) above sea level, the daily average in July is around 13 °C (55.5 °F) in the far north, 15 °C (59 °F) in the centre-north and 20 °C (68 °F) in the south, while at 1,000 metres (3,300 feet), it goes 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 the lowest altitudes, around a thousand metres or less, are not very large; so in most of Mongolia the summer has generally cool nights (sometimes even cold) and pleasant days, even though in the whole country, heat waves with peaks of 35/37 °C (95/99 °F) are possible, at least below 1,500 metres (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), in which the ground below a certain depth remains frozen throughout the year, and makes it difficult to build houses and infrastructures, and to dig for extraction of raw materials.