in +季节指的是抽象的季节,不特指.比如：Most people like to swim in summer,but some are fond of swimming in winter.大多数人喜欢夏天游泳,有些人喜欢冬天游.in the 季节指某个特定的季节.比如：I will go to Tibet in the summer.为了强调也会说“in this summer”,不过人们更习惯省掉in.