Algeria covers 2,381,741 square kilometers, making it the largest country in Africa and the tenth largest in the world. The nation sits on the northern edge of the African continent, bordered by the Mediterranean Sea across 998 kilometers of coastline to the north. Tunisia lies to the northeast, Libya to the east, Niger and Mali to the south, Mauritania and Western Sahara to the southwest, and Morocco to the west. This geographic position places Algeria at the intersection of Mediterranean, Saharan, and West African climate zones, creating distinct environmental regions that transition dramatically from north to south.
The Sahara Desert dominates Algerian territory, occupying approximately 80 percent of the country's total area. This vast expanse begins roughly 150 kilometers south of the Mediterranean coast and extends southward to the borders with Niger and Mali. Within the Algerian Sahara, the Grand Erg Occidental and Grand Erg Oriental form two massive sand sea systems, each covering tens of thousands of square kilometers with dune fields that shift continuously under wind action. The Grand Erg Occidental spans approximately 78,000 square kilometers in western Algeria, while the Grand Erg Oriental covers roughly 140,000 square kilometers in the east. These ergs contain some of the highest sand dunes in the Sahara, with individual dunes reaching heights of 430 meters in certain locations. Between and around these sand seas lie vast stone deserts called hamada and gravel plains called reg, where exposed bedrock and scattered stones dominate the landscape.
The Atlas Mountains form two parallel ranges that run roughly east-west across northern Algeria. The Tell Atlas, the northernmost range, extends approximately 1,500 kilometers from the Moroccan border in the west to the Tunisian border in the east, reaching elevations between 1,200 and 2,300 meters. Mount Lalla Khadidja, located in the Djurdjura massif within the Tell Atlas, stands at 2,308 meters and represents the highest peak in northern Algeria. The Saharan Atlas runs parallel to the Tell Atlas roughly 200 kilometers to the south, creating a second mountain barrier between the Mediterranean-influenced north and the Sahara. Djebel Chélia in the Aurès Mountains, part of the Saharan Atlas system, reaches 2,328 meters elevation. Between these two ranges lies a series of high plateaus at elevations between 900 and 1,200 meters, characterized by semi-arid steppe vegetation and seasonal salt lakes.
The Hoggar Mountains, also called the Ahaggar, rise in southern Algeria approximately 1,500 kilometers south of Algiers. This volcanic mountain range covers roughly 550,000 square kilometers, though the central massif itself occupies a more compact area. Mount Tahat, the highest peak in Algeria, stands at 2,908 meters elevation within the Hoggar range. The mountains formed from Precambrian basement rock overlain by later volcanic activity, creating dramatic landscapes of weathered granite peaks and volcanic plugs. Temperatures in the Hoggar region can drop below freezing during winter nights at elevation, creating a stark contrast with daytime highs that frequently exceed 35 degrees Celsius even in winter months.
The Tassili n'Ajjer plateau extends across southeastern Algeria, covering approximately 72,000 square kilometers at elevations between 1,000 and 2,000 meters. This sandstone formation features deeply eroded canyons, natural rock arches, and thousands of prehistoric rock art sites. The plateau receives slightly more precipitation than surrounding lowland desert areas due to orographic effects, supporting limited vegetation in wadis and sheltered locations. Annual rainfall on the Tassili plateau averages 50 to 80 millimeters, compared to less than 25 millimeters in adjacent lowland areas.
Algeria's river systems drain either northward to the Mediterranean or into closed basins within the interior. The Chelif River, at approximately 700 kilometers in length, represents Algeria's longest river. It rises in the Saharan Atlas near the town of Aflou, flows northeast through the Tell Atlas, then turns northwest before emptying into the Mediterranean Sea near the town of Mostaganem. The Chelif basin drains roughly 43,750 square kilometers. Flow varies dramatically between seasons, with peak discharge during winter and spring months following rainfall in the Tell Atlas. Many rivers in northern Algeria flow year-round in their upper reaches but become intermittent streams in lower sections during summer months.
Interior drainage basins in the Saharan portion of Algeria contain numerous seasonal lakes called chotts or sebkhas. Chott Melrhir, located in northeastern Algeria near the town of Biskra, forms the largest of these salt lakes. The chott sits at 40 meters below sea level and extends across approximately 6,700 square kilometers when filled seasonally. Water depth fluctuates from completely dry to several centimeters deep depending on seasonal rainfall and runoff from the Saharan Atlas. Salt crusts several centimeters thick form during dry periods, creating a white expanse visible from considerable distances. Temperatures at Chott Melrhir have been recorded above 50 degrees Celsius during summer months.
Northern Algeria experiences a Mediterranean climate characterized by hot dry summers and mild wet winters. Algiers, situated on the Mediterranean coast, receives an average annual precipitation of approximately 600 to 750 millimeters, with roughly 80 percent falling between October and April. January temperatures in Algiers average 11 to 12 degrees Celsius for daily lows and 15 to 17 degrees Celsius for daily highs. July and August temperatures average 20 to 22 degrees Celsius for daily lows and 28 to 30 degrees Celsius for daily highs. Coastal areas benefit from maritime moderation, preventing the extreme temperature variations found inland.
The Tell Atlas and Saharan Atlas ranges receive higher precipitation totals than surrounding lowlands due to orographic lifting of moisture-bearing air masses from the Mediterranean. Mountain locations at elevations above 1,500 meters typically receive between 400 and 1,000 millimeters annually, with the highest elevations occasionally exceeding 1,000 millimeters in favorable years. Snow falls regularly on peaks above 1,200 meters during winter months, with snow cover persisting for several weeks or months at the highest elevations. Djurdjura National Park in the Tell Atlas receives regular winter snowfall, with snow depths occasionally exceeding one meter at elevations above 2,000 meters.
The high plateaus between the Tell Atlas and Saharan Atlas experience a semi-arid climate with cold winters and hot summers. Annual precipitation ranges from 200 to 400 millimeters, falling primarily during winter and spring months. Temperature extremes intensify with distance from coastal moderation, with winter lows dropping to minus 5 to minus 10 degrees Celsius and summer highs reaching 38 to 42 degrees Celsius. Diurnal temperature variation increases significantly compared to coastal areas, with differences of 20 to 25 degrees Celsius between day and night temperatures common throughout the year.
The Saharan region of Algeria experiences hyper-arid desert climate with minimal and highly irregular precipitation. Most locations receive less than 100 millimeters annually, with many areas averaging below 25 millimeters. Rainfall events occur unpredictably, with individual years sometimes passing without measurable precipitation followed by sudden intense storms that deliver months worth of average rainfall in hours. Tamanrasset, located in the Hoggar Mountains at approximately 1,400 meters elevation, receives an average of 45 to 50 millimeters annually. In Salah, situated in central Algeria at 280 meters elevation, averages approximately 15 to 20 millimeters per year.
Saharan temperatures reach extreme levels during summer months. Ouargla, located in northeastern Sahara at 141 meters elevation, regularly records July temperatures above 45 degrees Celsius, with absolute maximums exceeding 50 degrees Celsius. The highest reliably recorded temperature in Algeria reached 51.3 degrees Celsius at In Salah on July 18, 2002. Winter temperatures in the Sahara vary dramatically with latitude and elevation. Northern Saharan locations experience mild winters with January averages around 10 to 12 degrees Celsius, while overnight lows occasionally drop below freezing. Southern locations like Tamanrasset experience more moderate summer temperatures due to elevation but colder winters, with January overnight lows regularly dropping below freezing.