Iran is one of the world's most mountainous countries. Iran has a variable climate. In the northwest, winters are cold with heavy snowfall and subfreezing temperatures during December and January. Spring and fall are relatively mild, while summers are dry and hot. In the south, winters are mild and the summers are very hot, having average daily temperatures in July exceeding 38 °C (100 °F). The Northern part of Iran is covered under thick rain forests and the eastern part consists mostly of desert basins.
More than one-tenth of the country is forested. The most extensive growths are found on the mountain slopes rising from the Caspian Sea. The land covered by Iran’s natural flora is four times that of the Europe’s.
With an area of 1,648,000 square kilometers, Iran ranks sixteenth in size among the countries of the world. Iran is about one-fifth the size of the continental United States, or slightly larger than the combined area of the contiguous states of California, Arizona, Nevada, Oregon, Washington, and Idaho.