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.
Most Popular. Thursday, September 22, is the date of the autumn equinox, the first official date of fall. The equinox marks the day when there are exactly 12 hours of sunlight, and marks the changing of the seasons. And with modern day science, we can narrow it down not just to the day, but to the very minute.