The Siberian High-pressure (HP) has various effects on Iran’s climate. Climate warming, especially in the last century, has raised the possibility of changes in the Outbreaks of the Siberian High-pressure extending toward Iran (OSH). In this study, to test the mentioned hypothesis, daily sea level pressure maps for 50 years (1972 to 2021) during the month in which the SH appeared more strongly in the monthly composite maps were downloaded from the NCEP/NCAR atmospheric data reanalysis database. The selection of this month was based on the highest central pressure intensity of the high (intensity index) and its greatest spatial extent (spatial index) compared to the other six months. The axes of the OSHs extending toward Iran were classified into four categories: “continuous and reaching,” “continuous and non-reaching,” “discontinuous and reaching,” and “discontinuous and non-reaching.” The design of their synoptic patterns showed a clear decrease in the frequency of “continuous and reaching” OSHs. Continuity refers to the directness of the OSH, and a reaching OSH is one that extends to the borders of Iran or penetrates into the country. Using two criteria— “the integrated advance of cold and dry air from the high-pressure center toward Iran” and “verification of the OSH entering or reaching Iran’s borders”—it was found that cold and dry air travels from Central Asia toward Iran through three main pathways: 1. The pathway of cold and dry air transfer from the western slopes of the Altai Mountains, then across the Turan Plain, and finally into central Iran. 2. The pathway of air transfer from the Dzungarian Plain in western China, then along the Tian Shan Mountains, through Afghanistan, and finally into the north of Sistan-va-Baloochestan Province. 3. The pathway of air transfer from the Kazakh steppes, through the Caucasus corridor (west of the Caspian Sea), reaching Azerbaijan, and extending along the Zagros Mountains. The frequency of OSHs has indicated a decline in five separated decades along all three pathways during the past half century. This decrease is more evident in the third pathway, namely the Caucasus corridor, which already had a lower frequency from the beginning.