Summer is the warmest of the four temperate seasons, between spring and autumn. At the summer solstice, the days are longest and the nights are shortest, with day-length decreasing as the season progresses after the solstice. The date of the beginning of summer varies according to climate, culture and tradition, but when it is summer in the southern hemisphere it is winter in the northern hemisphere, and vice versa. In areas of the tropics and subtropics, the wet season occurs during the summer. Tropical cyclones develop and roam the tropical and subtropical oceans during the summer. In the interior of continents, thunderstorms can produce hail during the afternoon and evening. Schools and universities have a summer break to take advantage of the warmer weather and longer days.