Summers are warm-hot and humid, with less wind than other seasons. During this season, a moderate wind often blows from the sea in the evenings which has a pleasant cooling effect on the city, in contrast to the more severe summer heat of nearby cities like Buenos Aires. Heat waves come with the north winds, which bring humid and hot air masses from the tropical interior of the continent. These warm periods are usually followed by thunderstorms, generated by cold fronts of the southwest that lowers temperatures considerably. This phenomenon is regional, and can occur several times all year long.