Summer's one of the four temperate seasons, marked by the warmest time of year with the longest days. Period The seasons are popularly considered to start on different dates in different cultures. When it's summer in the southern hemisphere it's winter in the northern hemisphere, and vice versa. From a purely astronomical viewpoint, the equinoxes and solstices would be the middle of the respective seasons, but a variable seasonal lag means that the meteorological start of the season, which's… (More on Summer)