Climate
Mostly desert; hot and humid along west coast; temperate in western mountains affected by seasonal monsoon; extraordinarily hot, dry, harsh desert in east. The weather can be chilly in areas where the elevation is high. Sana'a for example is at an elevation of over 7,200 feet. During the winter months, the temperatures can fall to zero during the night.
Landscape
Narrow coastal plain backed by flat-topped hills and rugged mountains; dissected upland desert plains in center slope into the desert interior of the Arabian Peninsula. The interior of the country is a highland dissected by valleys. Yemen can be divided into five regions:
Coastal Plain: The Tihamah coastal plain is a low-lying flat plain that has areas with very fertile soil from the streams from the mountains emptying into it. Some of the hottest places on Earth are in Tihamah. Most of its towns are coastal because the salty sea air can lessen the effect of the heat.
Western Highlands: The coastal plain ends abruptly at the western mountains, where monsoon rains coming from Africa gain strength across the Red Sea and the clouds coming in get tangled by the jagged peaks of the Western mountains and precipitate all of whatever the clouds hold. Some areas in the western highlands, notably Ibb and Ta'izz, get rainfall similar to rainforests, supporting fertile land great for coffee, qat, wheat, and sorghum. Moutains here are known to have lengthy ascents; most mountains pop out of land 2,000 feet above sea level to 7,000-10,000 foot peaks. Notable peaks include Jabal Sumarah, Jabal Ba'dan, Jabal Sabir, and Jabal Ad Dukayik, all about 10,000 feet high.
Central Highlands: This is more of a plateau with rolling hills atop it, for the mountains are less jagged and get less precipitation because most of it is released onto the Western Highlands. Some of the highest mountains of the Arabian Peninsula can be found here, including the legendary Jabal an Nabi Shu'ayb near the capital Sana'a, at about 12,000 feet above sea level. Some areas in the central highlands have extremely fertile soil, like in Dhamar, and temperature in the central highlands are extreme also. Diurnal temperatures are the highest in the world, with daytime highs of around 80°F while during the night they can dip to below freezing. Most of the central highlands, other than the mountains, is above 7,000-8,000 feet high.
Central Plateau: As a gradual descent from the central highlands begins, it eventually levels off at a 3,000-5,000 foot plateau that is bisected by valleys and wadis, or streams. This terrain is not as rough as the central or western highlands, but vegetation is only possible in the valleys or near wadis, for they provide a lot of irrigation water from precipitation that only occurs in the remote areas. Flash floods are very common here. This extends from Shabwah though Hadhramaut and Al Mahra, continuing into Dhofar in Oman, which also revered by many Yemenis as part of Greater Yemen, not to mention also Najran, Jizan, and Asir in Saudi Arabia.
Desert: Rub Al-Khali, aka the Empty Quarter, the most treacherous desert in the world, and also the largest expanse of sand in the world, is in northestern Yemen, southeastern Saudi Arabia, and northwestern Oman. It recieves no rain at all for periods of years, and little to no vegetation does or can exist. Temperature can reach 61°C 142°F
Understand
Yemen is a difficult country to get around, but the rewards for the perseverent tourist are an unforgettable experience, populated with very friendly and open hosts. Despite being adjacent to Saudi Arabia and on the same peninsula as the United Arab Emirates, Yemen is definitely a place apart.