There is a vastly extended network of rivers in Iran most of which seasonally are filled with water. Some permanent rivers run from the Alborz or the Zagros to the Caspian Sea, Persian Gulf and Oman Sea.
Iran has a variable climate. In the northwest, winters are cold with heavy snowfall and subfreezing temperatures during December and January.
Christmas in Iran is known as the Little Feast. For the first 25 days of December, a great fast is observed, during which no meat, eggs, milk, or cheese is eaten.