Expats living in Iran will have to contend with a semi-arid climate. While the north of Iran is a subtropical region, the rest of the country has long hot summers and short cool winters. 

Iran is typically hot and dry, but it also has subfreezing temperatures and heavy snowfall during winters, especially in the northwest. The Caspian Coast experiences steady rainfall throughout the year.

Spring in Iran coincides with Norwuz, the Persian New Year, and lasts from March to May. This time of year is cool, with temperatures rapidly rising towards summer. Spring is a relatively short season and expats can expect fluctuating weather patterns with some rain too.

Summer in Iran is the longest season and lasts from late May to September. It is hot and dry except on the Caspian Coast where rainfall starts as early as mid-summer and lasts through to winter’s end. Summer temperatures rarely exceed 84°F (29°C) in most of the country, but can rise as high as 100°F (38°C) in the east and desert areas.

Autumn in Iran is short, lasting only for October to November. Temperatures begin to drop and rainfall arrives in most parts of the country by November.

Winters in Iran are cool, especially in the northwest where the temperature drops below freezing and it snows, often heavily. From December until mid-March, the weather will remain cool and tends to stay below 50°F (10°C), while occasionally dropping below 32°F (0°C). This is also the wettest time of year.

A major concern for expats in Iran is the combination of humidity and heat. Heat exhaustion is a threat to unprepared or sickly residents and can be fatal. In addition, sudden violent storms can cause property damage and injury, and dust storms can result in fatalities. There are also frequent earthquakes in Iran. These are often damaging and lethal, especially when occurring close to Tehran. 

Two final environmental considerations for expats in Iran to be aware of are pollution and water security. The level of pollution in cities such as Tehran will adversely affect those with sensitive respiratory systems. Water availability is also a pressing current and future problem. To mitigate these challenges, it's best to prepare as much as possible beforehand.