单项选择题

E
Most of the Yellowstone National Park is above 2,275 meters. Yellowstone’s weather is very changeable. In summer, it may be warm and sunny with temperatures in the high 70s. At night in any given month, the temperature may drop close to freezing. So it is best to come prepared for cold evenings and mornings, especially if you are camping or hiking (立足). When you leave your camp, please be prepared for a possible sudden storm and wind.
A sunny warm day may become very stormy with wind, rain and sometimes snow. Without enough clothing and equipment, and easy day-hike or boat-trip can turn into a battle against nature。

According to the text, the relative dry season is in（）

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