World's largest hot desert. Located in north Africa and covers over 3,500,000 square miles (9,000,000 sq km) or roughly 10% of the continent. Mean temperature over 30 degrees C. Variations may also be huge, from over 50 degrees C during the day, to temperatures below 0 at night in summer.
Fall begins (Northern H.) History. Fall begins in the Northern Hemisphere when the Sun is perpendicular to the equator. This day has equal hours of day and night. The first day of Fall is also called the Autumnal Equinox. In many areas it coincides with harvests. The first day of Fall happens between each year between September 22 and 24.
When does it start? Since 2008, the National Weather Service has decreed a monsoon season from June 15 to September 30, but it still keeps track of the monsoon start by a measure it used from 1949 until 2008 â the first of three consecutive days with an average dewpoint of 54 or above.