What factors create major differences in climate across Iran?

The climate of Iran is highly diverse, ranging from subtropical to subpolar, due to several interacting geographical and meteorological factors. The primary influences creating these variations include:1

• Elevation and Latitude: These play a significant role in determining temperature fluctuations across the country.1
• Mountain Ranges: The Alborz Mountains and Zagros Mountains act as critical barriers. The Alborz range, for instance, traps moisture from the Caspian Sea, creating a humid, semitropical climate on its northern slopes while leaving the southern side arid.12
• Maritime Influences: Proximity to water bodies like the Caspian Sea, the Persian Gulf, and the Mediterranean Sea influences moisture levels and pressure systems.1
• Seasonal Winds: Patterns such as the shamāl and other regional winds significantly impact local weather conditions.1
• Proximity to Deserts: The presence of arid regions contributes to extreme temperature variations and low precipitation in central and eastern parts of the country.13

These factors result in sharp contrasts, such as the lush, high-precipitation Caspian region versus the dry, hot conditions of the Iranian plateau.12