Yemen is roughly rectangular, stretching 1,500 kilometres from east to west and 350 kilometres from north to south, and covers an area of 528,000 square kilometres; it is slightly smaller than France, Afghanistan, or Somalia, and slightly larger than Iraq, Spain, or Morocco. Yemen's northern neighbour, Saudi Arabia, is four times larger, while its eastern neighbour, Oman, is about half its size.

Yemen has several climates. Western Yemen benefits from monsoon rains, which fall mainly in late spring and at the end of summer. Most of the rain falls in the mountains, with an annual maximum of a 1,000 millimetres in the southern mountains, decreasing gradually to an average of 400 millimetres in the northern mountains. Temperatures in the mountains vary with altitude and season, with an average of 16°C and frosty winter nights in the higher mountains. The Tihama coastal strip, by contrast, is always hot and is very humid during the rainy season, a climate similar to that across the Red Sea, in Eritrea and Somalia. The eastern desert has a dry climate, with heavy but sporadic rains and frosty nights.