Despite the general dry trend for a sizable part of the country, for the rest the climate is surprisingly varied. 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). On the Khuzestan plain, summer heat is accompanied by high humidity.
Iran possesses an extremely diverse fauna and flora, partly because of its great range of habitats - from permanent snows to deep deserts and from lush deciduous forests in the north to palm groves and mangroves in the south - and partly because of its position at a crossroads between three major faunal regions. The greater part of the country is situated in the Palearctic Region, with typically Western Palearctic species predominating throughout the northwest, west and central parts of the country and some typically Eastern Palearctic species extending into northeastern Iran in the highlands of Khorasan. In southern Iran, two other faunal regions have a pronounced influence: the Indo-malayan Region in the southeast, and the Afro-tropical Region in the extreme southwest. About 125 species of mammals (Harrington, 1977; Eetemad, 1986) and 500 species of birds (Scott et al., 1975; Mansoori, 1995) have been recorded, while at least 270 species of fish (including 33 endemic species) are known from the Persian Gulf and Caspian Sea. A recent check-list records over 1,000 species of fish as being known to occur or potentially occurring in Iranian fresh and salt waters.
Botanically, Iran forms a bridge between four major phyto-geological regions: the Irano-Turanian, Saharo-Arabian, Euro-Siberian and Sudanian (Zohary, 1973). It is also one of the largest speciation centers of the Holarctic desert flora, with Irano-Turanian species predominating. The total number of plant species present has been variously estimated at between seven thousand and ten thousand, about 20% of which are endemic.
According to FAO reports , the major types of forests that exist in Iran and their respective areas are:
• Caspian forests of the northern districts (3.3 million ha)
• Limestone mountainous forests in the northeastern districts (Juniperus forests, 1.3 million ha)
• Pistachio forests in the eastern, southern and southeastern districts (2.6 million ha)
• Oak forests in the central and western districts (10 million ha)
• Shrubs of the Kavir (desert) districts in the central and northeastern part of the country (1 million ha)
• Sub-tropical forests of the southern coast (500,000 ha)
Visiting Religious Sites
Although no trip to Iran would be complete without a glimpse at the stunning architecture and somber environments of its mosques or holy shrines, many travelers are daunted by the prospect of walking into the foreign world of a mosque. Don't let these fears stop you, Iranians are welcoming and will understand any unintended breach of protocol.
Some mosques, and most holy shrines, require women to be wearing a chādor before entering the complex. If you don't have one, there are sometimes kiosks by the door that lend or hire chādors. It is better for men to wear long-sleeved shirts inside a mosque or shrine, though this is not mandatory.
Shoes are not worn within prayer areas of a mosque or shrine. Busier mosques have free shoe repositories where you trade your shoes for a token. Also try to avoid mosques on the holy day of Friday and don't photograph a mosque while prayers are taking place.
Holy shrines, like those in Mashhad and Qom, are usually off limits to non-Muslims, although the surrounding complexes are usually OK. Always ask first before you enter a room you are unsure of.