Iran Full Year Climatology Overview CONVENTIONS: The spelling of place names and geographical features are those used by the National Imagery and Mapping Agency (NIMA). All distances are in nautical miles (NM) and kilometers (km), except for visibility, which is in statute miles and meters. Elevations are in feet above mean sea level (MSL), with a metric conversion following. Temperatures are in degrees Fahrenheit (F) and Celsius (C). Wind speeds are in knots. Cloud bases are above ground level (AGL) unless otherwise stated; tops are above mean sea level (MSL). Precipitation amounts are in inches, with a millimeter (mm) or centimeter (cm) conversion following. Precipitation values given are liquid equivalent unless stated otherwise. Standard pressure levels are expressed in millibars (mb). Time is reported either in Coordinated Universal Time (UTC) (also known as Zulu or Z), or Local (L). General Weather. Iran has an arid to semiarid climate. Summers are intensely hot, except in the mountains, while the winter is cool to cold, except in the coastal lowlands. During winter, the weather pattern is constantly changing due to the frequent passage of migratory systems. During summer hot, dry, and often dusty conditions prevail. Sky Cover. The cloudiest time of the year is winter, but low ceilings are infrequent except in the mountains. Summer skies are mostly clear. Visibility. Visibility is generally good except in arid regions, where blowing dust and sandstorms cause reduced visibility. In addition, intense heating of the desert surface produces mirages and shimmers that reduce visibility to a few hundred yards along the surface. Winds. Surface winds exceed 20 knots 10 percent of the time. The shamal winds of the Persian Gulf coast and 'winds of 120 Days' of eastern Iran are well-known here. Both are strong winds that are hot, dry, and dust filled; strong gusts and dust devils are common; 50-55-knot gusts may occur. Precipitation. Precipitation falls year-round near the Caspian Sea, particularly in the west where annual amounts exceed 50 inches (1,270 mm). The interior plains of Iran get less than 5 inches (127 mm) of rainfall per average year. Throughout the remainder of Iran, most precipitation occurs in winter and spring, with the largest amounts in the mountains. The permanent snow line during winter is near 5,000 feet (1,520 meters) across most of northern Iran. Temperature. Winter temperatures along the southern coast are 55F to 62F (13C to 17C) in the morning hours and 78F (26C) in late afternoon. Temperatures in north central Iran range from 23F (-5C) in the morning to 43F (6C) in the afternoon. Winters are very cold in the mountains; these temperatures range from 15F (-9C) in the morning to 43F (6C) in the afternoon. Summer afternoon temperatures vary from 85F (29C) along the Caspian Coast to over 110F (43C) at the head of the Persian Gulf. The morning temperatures vary from 65F to 75F (18C to 24C) along the Caspian Coast and north central Iran to 78F to 82F (26C to 28C) along the southern coast. Low humidity, except along the coastal strips, helps reduce the heat stress on personnel. POINT OF CONTACT: Address questions and comments pertaining to this narrative to AFCCC/DOC5, 151 Patton Avenue, Room 120, Asheville, NC 28801-5002. Telephone: DSN 673-9007 or Commercial (828) 271-4234. E-mail
DOC5@afccc.af.mil Approved for public release: distribution is unlimited June 1988