چکيده

One of temperature status is high temperatures and occurrence of hot days. Surveying hot days and their atmospheric mechanism together with this event is an inevitable necessity regarding the importance of this temperature status. In the present paper,  it is tried  to recognize, classify and analyze  the widespread hot days of Iran. For this purpose, two databases have been used in this study; Firstly, data base network of the state maximum temperature  , these data are the outcome of interpolation of the beginning of   1961 up to the end of  2007. The second is atmospheric data  including sea surface pressure( Hectopascal), zonal and meridian wind(M/S) and geopotential height(m). to study these data, an area  between 10 °  of West longitude  up to  120 ° of East longitude  and 0° up to 80 °  of north Latitude was considered. During the statistical  period ,1539 hot days have been identified. These days has been classified in to 4 categories by using cluster analysis. Analysis of atmospheric conditions together with these days showed that together with  forming warm days , the  regional  low pressure and negative anomaly of pressure is possible in the country. So the wind  direction from southern areas especially Saudi Arabia, Iraq and Africa in lower levels of the earth and even middle of the atmosphere , which is due to the height increase on Iran, has been observed. Surface  and higher elevation heating  has made the atmospheric sustainability, because the temperature difference of the two elevations and consequently the thermal vacation is decreased and stability of temperature status is expected.