Most of the districts in this climate have subtropical weather. Because the wind from other lands is blowing in hot and dry climate from southeast and northeast toward the tropic, air is so dry. After passing along big continents, these winds lose their humidity and also because of moving form upper layers of the atmosphere to the surface of the earth they become hot and dry.
These two reasons which make weather of this districts hot and dry, made native architects consider the climate in building design.
Severe sunshine in hot and dry climate produces 700-800 k.cal/h/m2 energy on horizontal surfaces and after increasing reflected ray from arid surface that released energy will get more severe. Most of the days in year sky is without cloud and because of moving the upper air layers near the earth surface fug, typhoon or dust occur.
temperature
Low humidity or lack of cloud existence leads to high temperature oscillation. Sunshine heats the ground surface temperature till 70oc but during the night this temperature rapidly decreases to 15oc and less. Of course, this frequent changing or oscillation temperature is only for surface of the ground.
But the temperature of the air per se does not have such an oscillation, nevertheless the amount of air oscillation temperature between day and night is 20oc. Air temperature in hot days of summer is between 40-50oc and at night reaches to 15-25oc.
Central Plateau which is the most extensive area in Iran and is surrounded by high roughness, regardless of the edges attached to the mountains and some independent internal area, are in hot and dry climate. Its special feature is severe cold of winter and hot and dry air of summer.
Semi-desert-like district
If you Imagine the central plateau of Iran and see it on the photo you can realize that the plateau is surrounded by sidehills and foothills of northern, southern and western mountains in addition some independent areas in the middle of plateau. Weather in the side of the mountains which are faced to the plateau is different from the weather in central flat surfaces because of height of these two areas, they can use the humid winds blowing in upper layers. In this reason we can say that hot and dry climate itself has been divided into different weather. Weather in these two regions that we mentioned is called semi-desert weather. Weather of cities like Tehran, Mashhad, Shiraz and Isfahan weather are counted as semi-desert weather.
desert-like district
Lack of humid winds in low height of the desert which includes central, eastern, southeastern part of the district causes the region to have dry. These regions have desert weather. weather of cities like Yazd and Zahedan weather are counted as desert.