Richard,
difficult to tell you when the best time, but I went through Mauritania early october, first through the desert from N'bhou to N'chott, then back and forth to Atar/Chinguetti/Terjit, and then further on to Senegal. The desert was no real problem re temp, because you're always pretty close to the sea so you get some colling effect from the sea. Same more or less for road down to Senegal. However road from N'chott to Atar was pretty hell, up to 80° (celsius!!) in the sun, no shadow, well, you can picture it more or less... region of Atar is better due to altitude. If you are there, you MUST visit oasis of Terjit, you will double appreciate it when it's hot...
Hope it helps you on your trip,
jef
|