Overview: It mostly belongs to temperate monsoonclimate and temperate continental climate in the northwest of China. This areais deep in the inland and far away from the sea. Moreover, due to the obstruction of the terrain to moist air flow, the region the temperate monsoonclimate only happens in the southeast of this region , and the temperate continental climate happens in the rest area of northwestern China. In winter,it is cold and dry, while in summer, it is very hot with little precipitation occur, decreasing from east to west.

Due to the dry climate, the temperature difference is quite large between the early morning and late night. In the large part of northwestern China it belongs to temperate zone and warm temperate zone. Turpan Basin is the hottest area in China in summer and Toksun has the lowest precipitation in China.

Here are some reference information of the climate for the main cities along the silk road.

Xi'an (the old capital of ancient China)

In Xi'an it has most of its annual precipitation from August to late October in the form of rain. It is featured with hot summers and cold, dry winters. Spring and autumn will be somewhat short and dry.
In Xi'an  the  temperate climate occurs very often which is influenced by the East Asian monsoon, classified under the Kippen climate classification assituated on the borderline between a semi-arid climate (BSk) and humid subtropical climate (Cwa). The Wei River valley is characterised by hot, humid summers, cold, dry winters, and dry springs and autumns. Most of the annual precipitation is delivered from July to late October. Snow occasionally falls in winter but rarely lasting for long. Dust storms often occur during March and April as in the city it rapidly warms up. The months in summer also experience frequently but short thunderstorms. The monthly 24-hour average temperature ranges from around the freezing mark in January to 26.6 °C (79.9 °F) in July, with an annual mean of 13.68 °C (56.6 °F). Extreme temperatures have ranged from -20.6 °C (-5 °F) to 42.9 °C (109 °F).

Lanzhou (named golden fort in the ancient time)

Lanzhou is situated at the upper reaches of the Yellow River where it emerges from the mountainsand it is the only provincial capital city which the yellow river runs through. It commands the approaches to the ancient capital area of Chang'an (modern Xi'an) in Shaanxi province from both the west and the northwest, as well as the area of Qinghai Lake via the upper reaches of the Yellow River and its tributaries.
Lanzhou is located in the temperate zone and enjoys a semi-arid climate with hot summers and cold and very dry winters. The monthly 24-hour average temperature ranges from -5.3 °C (22.5 °F) in January to22.4 °C (72.3 °F) in July. The average annual temperature is 9.75 °C (49.6 °F),while annual rainfall is 315 millimetres (12.4 in), almost all of which falls from May to October. It is so dry that snow is extremely rare in winter time. Sunshine is generous, with no month having less than 50% of the potential, but not particularly abundant, averaging 2,424 hours annually.
Serious air pollution in the city means that it has some of the worst air quality of any city nationally. According to the Blacksmith Institute, Lanzhou is one of the 30 most polluted cities in the world, with its TSP (total suspended particle)] rating 247% above that of the Gansu State recommendation. Air quality is so poor that at times one cannot see Gao Lanshan, the mountain rising straight up along the south side of the city. At one point, one controversial suggestion was put forward to bulldoze a mountain adjacent to the city, in order to let fresh air into the bowl where Lanzhou is situated. It was suggested on the premise that the surrounding mountains block a free flow of air in the city. The city is located in a narrow river valley with an unfortunate curve causing it to be hemmed in with no free air flow. Lanzhou is also the home of many factories, including some involved inpetroleum processing, and suffers from large dust storms kicked up from the Gobi Desert, especially in the winter and spring. In 2011, using Chinese statistics, the World Health Organization reported that Lanzhou has the worst air quality (annual mean PM10 ug/m3 of 150) among 11 western Chinese cities, and is even worse than Beijing with its reading of 121.
The reach of the Yellow River at Lanzhou carries a high load of silt, giving the river its characteristic muddy appearance; however water quality in this reach is better than the "fetid outflow that barely passes for water two hours downstream".

Dunhuang ( named Sha zhou in ancient time)

Dunhuang, being surrounded by high mountains,Gobi desert and sanddunes, has an arid and continental climate. The annual average temperature is 9.48 °C (49.1 °F), but the monthly daily mean temperature ranges from 24.6 °C (76.3 °F) in July down to -8.3 °C (17.1 °F) in January. In the city it is extremely hotin summer and cold in winter, and usually there is sharp temperature differences between day and night. Precipitation occurs only in trace amounts and quickly evaporates. The annual average rainfall is only 39.9 mm, but the capacity of evaporation is around 2200 mm.

Turpan (called fire state in ancient time)

Turpan is located about 150 km (93 mi) southeast of Urumqi,the capital city of Xinjiang.It is in a mountain basin and on the northern side of the Turpan Depression, with an elevation of 30 m (98 ft) above sea level. Outside of Turpan is a small volcanic cone, the Turfan volcano,it is said that the volvano has erupted in 1120 AD. as described in the Song Dynasty.
In Turpan it has a harsh, drastic, cold desert climate with long and very hot summers, winters that are quite cold but short, and  spring and autumn are short . Annual precipitation is very low, amounting to only 15.7 millimetres(0.62 in). The monthly 24-hour average temperature ranges from -7.6 °C (18.3°F) in January to 32.2 °C (90.0 °F) in July; the annual mean is 14.4 °C (57.9°F).
Extremes have ranged from -28.9 °C (-20 °F) to 48.1 °C (119 °F), although areading of 49.6 °C (121 °F) in July 1975 is regarded as dubious.
However, the very heat and dryness of the summer, when combined with the ancient system of irrigation in this area, allows the countryside around Turpan to produce great quantities of high-quality fruit.

Urumuqi (the capital city of Xinjiang)

In Urumuqi a semi-arid climate prevails, with very large difference between summer and winter. During hot summers, it is with a July daily averageof 23.7 °C (74.7 °F), and in cold winters,it is with a January daily average of-12.6 °C (9.3 °F). The annual average temperature is 6.90 °C (44.4 °F).

The city is semi-arid, with summers slightly wetter than winters, yet sunny weather is more likely in the warmer months, and relative humidity is the lowest during summer. Its annual precipitation is about 290millimetres (11.4 in). Extreme temperatures have ranged from -41.5 °C (-43 °F)to 42.1 °C (108 °F).

Kashgar (named Shu le in ancient time)named Shu le in ancient time)

Kashgar features a desert climate with hot summers and cold winters, with large temperature difference between those two seasons. The monthly 24-hour average temperature ranges from -5.3 °C (22.5 °F) in January to 25.6 °C (78.1 °F) in July, while the annual mean is 11.8 °C (53.2 °F). Spring is long and arrives quickly, while fall is somewhat short in comparison.

Kashgar is one of the driest cities on the planet, averaging rainfall is only 64 millimetres (2.52 in) per year. The  wettest month in the city, July, only reaches on average 9.1 millimetres (0.36 in) of rain. Because of the extremely arid conditions, snowfall is rare, despite it is very cold in the winters. Records have been done as low as -24.4 °C (-12 °F) in January and up to 40.1 °C(104.2 °F) in July. The frost-free period averages 215 days.