Weather: Mali, Burkina, Chad, Mauritania ,Niger

As sprawling as it is – Mali is nearly twice the size of Texas – this semi-arid country and its neighbours share a common climatic language. The yearly arrival and departure of the ITCZ and its rain is what divides the southern part of Mali from the harsher desert regime to its north. The same holds true for Niger and Chad to the east and most of Mauritania to the west. The slow onset of the monsoon begins in the spring across the southern Sahel with a tantalizing hint of rain in the midst of oppressively hot and increasingly muggy weather (highs often top 38°C/100°F). The north is less humid but even more blazingly hot. By mid-summer, the tongue of moist air marking the ITCZ has pushed up to roughly 20°N. During July and August, locations south of 13°N – including southern Mali and Burkina – feel much more like the humid tropics, with rains every day or two and slightly more tolerable heat than in the spring. The belt from around 13° to 18°N remains scorching, but has just enough moisture for spotty showers and thunderstorms, which might total over 150mm/6in in a good summer or almost nothing in a bad year (like those of the 1970s and 1980s that ravaged the Sahel with drought). Most of the summer rains across the Sahel are delivered by easterly waves and squall lines. These great bands of storms originate after easterly flow is funnelled through the mountains of Chad and encounters the humid southwesterlies south of the ITCZ. Each line of storms brings a quick, dramatic bout of gale-force wind and heavy rain, followed by a pleasant cooldown for a few hours. The wet season ends quickly across the Sahel, and December and January can be a treat: rain-free, cool at night, and warm by day. However, if the prevailing northeast winds intensify beyond about 55kph/34mph, they can generate enough dust to produce winter's down side – the irritating harmattan. Harmattan dust sometimes extends all the way to coastal Mauritania, where sea breezes normally take a slight edge off the year-round heat.