The highlands enjoy a temperate, rainy summer with an average high temperature of 21 °C (69.8 °F) and a cool, moderately dry winter with temperatures occasionally dipping below 0 °C (32.0 °F). The climate of the Tihamah (western coastal plain) is tropical; temperatures occasionally exceed 54 °C (129.2 °F), and the humidity ranges from 50 to 70 percent. Rainfall, which comes in irregular heavy torrents, averages 130 millimetres (5.12 in) annually.
In Aden the average temperature is 25 °C (77.0 °F) in January and 32 °C (89.6 °F) in June, but with highs often exceeding 37 °C (98.6 °F). Average annual rainfall is 127 millimetres (5 in). The highest mountainous areas of southern Yemen receive from 520 to 760 mm (20.5 to 29.9 in) of rain a year. Some areas of the western highlands, most notably Ibb and Ta'izz, receive from about 1,000–1,500 millimetres (39.4–59.1 in) of rain each year.
The capital, Sana'a, receives around 300 mm (11.8 in) a year, It is not uncommon for the northern and eastern sections of the country to receive no rain for five years or more. The Wadi Hadhramaut in the eastern part of Yemen is arid and hot, and the humidity ranges from 35 percent in June to 64 percent in January. Yemen is dry in the east and humid in the west.