Because of its size, topography and altitude, Iran experiences great climatic extremes. Winters (December to February) can be unpleasantly cold, especially in the north and west, and in most of the rest of the country the nights are very cold. In summer (June to August) temperatures as high as 50°C are nothing out of the ordinary along the Persian Gulf coast and southern provinces.
Regular rainfall is more or less restricted to the far north and west – the area north of the Alborz Mountains receives an annual average of about 1300mm of rain, but although year-round cloud helps keep summer temperatures manageable the high humidity makes summer pretty muggy on the Caspian coast. In western Iran winter temperatures are regularly well below zero and snow frequently remains until early spring.
 it’s best to avoid the Persian Gulf coast between early May and mid-October, when the double whammy of high temperatures and oppressive humidity take much of the fun out of travel. Further inland, summer temperatures are very warm indeed, but low humidity makes life more bearable.
When to go
When deciding when to go to Iran you must first work out where you’d like to go. Temperatures can vary wildly: when it’s -5°C in Tabriz it might be 35°C in Bandar Abbas, but for most people spring and autumn are the most pleasant times to visit. At other times, the seasons have advantages and disadvantages depending on where you are. For example, the most agreeable time to visit the Persian Gulf coast is during winter, when the humidity is low and temperatures mainly in the 20s. At this time, however, the more elevated northwest and northeast can be freezing, with mountain roads impassable due to snow. Except on the Persian Gulf coast, winter nights can be bitterly cold, but we think the days (often clear and about 15°C in much of the country) are more pleasant than the summer heat.
And when we say ‘heat’, we mean it. Between May and October temperatures often rise into the 40s, and in the deserts, southern provinces and along the Gulf coast, very little is done between noon and 4pm or 5pm. For women, who need to wear head coverings whenever they’re outside, summer can be particularly trying.