The climate is characterized by extremes in temperature and by meagre and irregular rainfall. Most of Mauritania is located in the tropics, and the weather is often very hot, although night time temperatures can dip below 7°C and as low as freezing point in the Sahara during the early morning.
Mauritania is a land about desert and ocean. It is of course no wonder that the main attractions for most tourists are the desert in Adrar and the Tagant areas around Atar, and the ocean in Banc d'Arguin a natural reserve with dunes ending in the sea, full of millions of birds and protected by UNESCO. The Adrar is exactly how you've always imagined the Sahara as: endless ergs dunes and regs rocky desert with tabular small mountains. Most tourists stay along the west coast of the country, although there are a few beautiful sights far into the interior rock formations in Aioun, for example. If you decide to travel off the beaten path, leave plenty of time to get around.
Mauritania is an Islamic Republic. Don't be afraid of this political status - most Mauritanians are not extremists, even if the majority of the people in the North are very conservative and quite reserved. Neither slavery, female genital mutilation, child labour nor human trafficking are rare and racism against people with darker skins is both open and prevalent. The Southern part of the country is filled with friendly people, and they are very welcoming, if a little unused to tourists.
Travelling to Mauritania is becoming easier, with charter flights from France to Atar through the winter months. Guides and tourist agencies are quite easy to find. However, Mauritania is not connected to the international banking system. Your Visa card will not work in the local ATM. However, there are now international ATM's at BNP and Societe Generale in Nouakchott, Atar and Nouadhibou. Otherwise, credit cards are accepted almost nowhere. It is easy to change euros, dollars and francs CFA in Nouakchott, however.