Algeria is a hot country, but the coastal region is pleasant for Europeans and North Americans most year through, while people originating from warmer regions, will only have to take the same kind of precautions as they do back home. The Sahara Desert, though, should only be travelled in, after serious consideration, where one's one health, as well as the season are evaluated.
In the north, in the Kabyle region, rainfall/snowfall is as high as 1,000 mm annually. Most parts of Sahara has years passing by without any rain at all. In the capital Algiers, in the north, at the coast, August is the warmest month, and January the coldest. Here the maximum/minimum temperature is 30°C/22°C in August, and 16°C/10°C in January. Western travellers will find May to October, as a period of nice summer. Algiers has relatively high humity, at around 60%. There is a good amount of rain falling over Algiers, most of it in winter, almost noting in summer. Annual rainfall exceeds 700 mm annually (about as much as Oslo, Norway).
In Tamanrasset, in the south, in Sahara, but up in cooling mountains, has June as the warmest month, and January as the coldest. Here the maximum/minimum temperature is 36°C/22°C in June, and 21°C/5°C in January. As the temperatures vay quite a bit from year to year, Tamanrasset offers in reality nice temperatures all year through, much due to low humidity, at around 20%. Tamanrasset has extremely little rainfall, counting to about 20 mm annually, so the city relies upon water coming down from the nearby Hoggar mountains.
Winds are an important part of Algerian climate, in winter often very pleasant, while they in summer can be in the shape of draw thaw wind, called Sirocco and Ghibli. These can be so frequent that they cover 50 days every year in the interior high land, while they cover 20 days in the coastal region.