The climate of valleys is synonymous with extremes of temperatures. In summer these places are quite hot, in winter bitterly cold. The following is a short description of this type of climate.
Valleys record extremes of temperatures in summer and winter. The more deep a valley is ,the more the fluctuation of temperature. This means that the valleys which are surrounded by very high mountains are susceptible to very large changes in temperature. The typical station of special interest both for holiday makers and meteorologists is the world famous Gilgit Valley in Northern Areas of Pakistan located not far away from the Shin door Pass, the centre of Annual Polo Festival. It is surprising to note that although it has a high latitude of about 36 degrees North, and an elevation of about 5000 feet above sea level but still temperatures up to 113 F (45 C) are common. During the night however the temperature falls to 60 F (16 C), a fall of 31 degrees Celsius! This is because Gilgit is surrounded by very high mountains which reach in height up to 20,000 feet. At night when the sky is clear, the surfaces of the mountains becomes much cooler due to re radiation of heat to the atmosphere which they have absorbed during the day. As the surface becomes cooler and cooler during the night, the air touching the slopes becomes very cold too. It also becomes dense and heavier as compared to the surrounding air. Under the action of gravity, the cold air is pulled down the slopes until it is accumulated in the deep valleys. This wind is the Katabatic wind, commonly known as the mountain wind. As this wind arrives from mountains situated high up, so it is very cold and brings down the temperature of the valleys considerably. Hence the nights of the valleys continues to be cool even in mid-summer. In the day, however, since the valleys are situated at low elevations as compared to the mountains, and these areas have a very clear atmosphere, they become quite hot by mid-day, especially when there is no cool air coming from any side.
In winter due to same effect, the valleys record temperatures which are several degrees below zero and are bitterly cold. It is usual for Gilgit to record temperatures up to 20 F in winter.
In short, it follows from the above discussion that the valleys have a large diurnal as well as seasonal range of temperatures. So next time you plan to visit these places in summer, be prepared to face extremely hot winds and chilly nights in the same season.