Algeria is a North African country four times as large as France. About one-sixth of the country, comprising the Mediterranean coastlands and the northern mountains, has a typical Mediterranean climate with winter rainfall. The rest of the country to the south of the Saharan Atlas Mountains is almost rainless and is part of the great Sahara desert.
Northern Algeria has a varied relief with two ranges of moderately high mountains: the Tell Atlas and the Saharan Atlas, separated by a region of elevated plains and interior basins, the Plateau of the Chotts. Climate and weather here vary locally depending on altitude. Rainfall is heaviest and most reliable along the Mediterranean coast and in the higher parts of the Tell Atlas where it varies from 400 mm/16 in to 800 mm/32 in per year. Most rainfall occurs between September and May with the heaviest and most reliable rains occurring from November to March. Above 900 m/3,000 ft precipitation often falls as snow and at the highest levels this may lie for several weeks. From May to September the weather here is generally settled and hot with almost continuous sunshine. During the rest of the year it is more changeable, with an alternation from warm sunny days and cool nights to disturbed periods with rain and cloud. The mildest weather in winter is to be found on the coast; this area also tends to escape the fiercest summer heat, except when a hot dry sirocco from the south carries the heat of the Sahara northwards. The table for Algiers is representative of the coast.
Inland the Hauts Plateaux and the Saharan Atlas have a rather more extreme continental type of climate with hotter summers and colder winters. Frost and snow occur here in winter and the nights can be very cold after quite warm days. The heat in summer frequently reaches levels typical of the Sahara but is made more tolerable by the low humidity. Over much of the area rainfall is rather low with a tendency to a double maximum, in autumn and spring. Immediately south of the Saharan Atlas there is a narrow belt of steppe country, similar to that in southern Tunisia. There is a definite wet season in winter but rainfall is low and unreliable. The table for Biskra is typical of this area on the fringe of the Sahara.
The Saharan desert region of Algeria has a climate that is virtually rainless. Occasional rain may fall in any month but the amounts are so small and unreliable as to make averages meaningless. In the extreme south of Algeria sporadic rainfall is more probable in the period June to September as the intertropical rain-belt, which affects West Africa at this time, occasionally spreads this far north. In the southeast of Algeria the great mountain mass of the Hoggar, rising to over 2,900 m/9,500 ft receives rather more rain which may fall at any season. The table for In Salah, in the centre of the Sahara, is representative of this vast desert region. Summer temperatures are consistently high but temperatures at night fall low enough to be quite tolerable. Winter nights in the Sahara can be chilly and frost is by no means unknown but the days are warm and sunny.
Algeria has a very sunny climate. In the north daily sunshine averages from five to six hours in winter and eleven to twelve in summer. In the Sahara they approach the maximum possible duration: nine to ten in winter and twelve to thirteen in summer.
In the Sahara strong winds occasionally raise dust and sand which can be dangerous as well as most unpleasant. During the hottest weather there is some danger of heat exhaustion, or even heatstroke, unless proper precautions are taken.
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