Iran is famous for its four-season weather. It is considered as one of few countries in the world where visitors may experience all four seasons in a part of the country all year long.
You can find four seasons at the same time through out the year in every corner of the country. At the time that summer starts in the southern and northern parts of the country close to the bodies of water (Caspian Sea in the north and Persian Gulf in south), you will be able to travel to the west to ski in snowy mountainous regions.
If you are planning to go to the west of the country and also the mountainous area, make sure you have a cardigan or a light jacket with you. If you are going to higher elevations, make sure you are prepared for a very cold temperature. It can get chilly even in the middle of August!