The climate of the region is temperate maritime, with hot, humid summers and short, cool winters, with the warm Kuroshio Current offshore having a moderating effect.

[3] During the late Heian and Kamakura periods, the town of Nirayama within the current borders of Izunokuni was the home of the Later Hōjō clan, who dominated Japanese politics in the 12th century.

The city of Izunokuni was created on April 1, 2005 from the merger of the towns of Izunagaoka, Nirayama and Ōhito (all from Tagata District).

Izunokuni has a mayor-council form of government with a directly elected mayor and a unicameral city legislature of 17 members.

The economy of Izunokuni is dominated by agriculture (strawberries and tomatoes) and by tourism related to the hot spring resort industry.