The Calendar for Day Time Temperature of Iran

In this study, the start and ending time of warm and cold periods of the year in Iran has been investigated. To this aim, the grid data of maximum daily temperature of Iran with spatial separation of 15×15 and time interval 21/3/1961 up to 20/3/1-2003 including 15705 days were extracted from Asfazari data base, second edition.Using the array of Iran’s day time temperature data of dimension 15705*7187, the long term mean of temperature was calculated and tabulated, the year was divided in two periods of warm and cold periods based on the long term mean of the temperature of each part of the country. Finally, the maps for the highest and lowest daily temperature start and ending dates of warm period and mean of daily temperature in cold period were calculated and plotted.The maps showed that, mean of Iran’s day time temperature is 25.2 Celsius degree. Warm period of Iran occurs from 18 April up to 25 October and the cold period starts from 26 October up to 17 April of the next year. Cold and warm periods do not start simultaneously all over Iran. At the south and south east parts of the country, the warm season starts earlier and ends later. The peak warm temperature in Iran occurs at different parts with a time interval of 70 days. While the peak cold occurs almost simultaneously with a time interval of 15 days all over Iran.