Mongolia is the world's 19th-largest country. The geography of Mongolia is varied, with the Gobi Desert to the south and with cold and mountainous regions to the north and west.
Most of the country is hot in the summer and extremely cold in the winter, with January averages dropping as low as 30 °C (22 °F). A vast front of cold, heavy, shallow air comes in from Siberia in winter and collects in river valleys and low basins causing very cold temperatures while slopes of mountains are much warmer due to the effects of temperature inversion.