en Environmental Health, Sciences, and Engineering Environmental Health, Sciences, and Engineering پژوهشي Original Article <div style="text-align: justify;"><span style="font-size:14px;"><span style="font-family:times new roman;"><strong>Background:</strong> The present study aimed to validate the thermal regions in Iran with an emphasis on the identification of the climatic cycles during the recent half-century.<br> <strong>Methods:</strong> Data on daily temperature were extracted for 383 synoptic stations of Iran Meteorological Organization. For the zoning of the temperatures of Iran, multivariate statistical techniques (cluster analysis and discriminant analysis) were applied. In addition, the verification of the areas that were identified by cluster analysis and discriminant analysis was performed using the silhouette analysis.<br> <strong>Results:</strong> Discriminant analysis and silhouette analysis could properly identify the thermal regions in Iran, and this claim was confirmed with 2% error. Moreover, the spectral analysis of the thermal regions indicated that the temperature of Iran in the first and second regions had a medium-term cycle or an occasional short-term cycle, while fluctuations were observed in the third and fourth regions, as well as 2-5-year short-term cycles.<br> <strong>Conclusion:</strong> According to the results, the temperature of Iran was affected by several factors in some regions with variable patterns, so that diverse short-term, long-term, and medium-term cycles were dominant in the thermal regions in Iran.</span></span></div> Cluster analysis, Discriminant analysis, Silhouette index (SI), Principal components analysis, Spectral analysis 1 8 http://jhehp.zums.ac.ir/browse.php?a_code=A-10-140-2&slc_lang=en&sid=1 Mustafa Solgimoghaddam m.solgimoqadam@gmail.com 10031947532846009663 10031947532846009663 No Department of Environmental Science, School of Science, University of Zanjan, Iran. Younes Khosravi khosravi@znu.ac.ir 10031947532846009664 10031947532846009664 Yes Department of Environmental Science, School of Science, University of Zanjan, Iran. Hossein Asakereh asakereh@znu.ac.ir 10031947532846009665 10031947532846009665 No Department of Geography, School of Humanities, University of Zanjan, Iran. Mehdi Doostkamian smehdi67@gmail.com 10031947532846009666 10031947532846009666 No Department of Geography, School of Humanities, University of Zanjan, Iran.