Algeria stretches from the Mediterranean Sea to the heart of the Sahara, and that sheer geographic span means the country doesn't have one climate so much as several layered on top of each other. Along the northern coast, where Algiers sits, the weather follows a classic Mediterranean pattern: mild, rainy winters and long, dry summers. Move inland past the Tell Atlas mountains and you hit the high plateaus, where continental air sharpens the winters and dries out the summers further. Push south into the Sahara and you enter a world of extremes, where daytime temperatures can be punishing but nights, in winter, drop surprisingly low. For most travelers, the coastal strip and the northern cities are the entry point, so the data here, measured in Algiers, gives a useful baseline for planning, though anyone heading to the desert or the Kabyle mountains should expect conditions to diverge considerably.
The year in Algeria divides fairly cleanly into a wet season running from roughly October through March and a dry season from June through September, with April, May, and early October acting as shoulder months that tend to offer the most agreeable conditions. November is typically the wettest month in Algiers, with around 102 mm of rain spread across about nine days, while July sees almost none, just 3 mm on average, with rain falling on perhaps a single day all month. Humidity stays in a fairly narrow band year-round, hovering between 67 and 79 percent as measured in Algiers, though it feels less oppressive than those numbers might suggest because the coastal breeze usually takes the edge off. The UV index climbs from a gentle 2 in midwinter to a peak of 9 in June and July, which is worth taking seriously if you plan to spend time outdoors.
What makes Algeria's weather interesting for travelers is that you can, with a bit of planning, find comfortable conditions somewhere in the country during almost any month. When the coast swelters in August, the Djurdjura mountains stay cooler. When winter rain soaks Algiers, the Saharan oases around
Ghardaia and Timimoun bask in dry sunshine and tolerable warmth. It rewards flexibility.