In the desert world, the seasons differ from one region to another. The Gohi ,which lies roughly between 35℃ and 55℃ north of the equator, is a good example of seasonal change. Four seasons are characteristic of the Gobi: spring, summer, fall, and winter, with usually a false spring at the end of winter. These seasons are distinct, with extremes of temperature, as much as 150 between the hottest day in summer and the coldest day in winter. Spring in the Gobi usually begins about the second week April. For 2 or 3 weeks there is a period of delightful weather, with warm, sunny days and not too much wind. But these are the days of false spring. About the first of May, the tail end of winter returns, and cold, blustery days of dustburdened winds are the rule then, until early or middle June. The latter part of June, for 2 or 3 weeks after the blowy end of winter is the real spring. It spreads its rather comfortable warmth over the desert, and occasional light rains help the desert grass to come along nicely. July, or sometimes mid-June to mid-August is summer. Hot days are the rule, but the nights are cool. Wind and dust again govern the desert, but this is the season when hard rains, if they come at all, are most likely to dump water on the plains. Fall usually may be recognized by the encouraging, bright days beginning in mid-August and lasting until mid-September or the first of October. This is the time of year when both men and beasts feel best in the Gobi. The clear air, bright sun, and frosty temperatures make you glad to be alive. Winter comes with a rush anytime after the middle of September. One day you may be enjoying a pleasant temperature near the eighties. But suddenly the air cools. In a few hours the temperature has slipped below 50; and a little later cold rain changes to snow and blustering wind. In this passage the author briefly describes ______.