Yanai is located in southeastern Yamaguchi Prefecture, at the base of the eastern coast of the Murotsu Peninsula. The city overlooks Mt. Kotoishi(Chūgoku 100 mountains) and portions are within the borders of the
Setonaikai National Park. The city area consists of coastal areas, inland areas (Ikachi and Hizumi areas), peninsulas and islands (Heigun Island), and more than half of the total area is mountainous and hilly. Urban areas are mostly on flat areas along the coast. In the northern inland area, and rural villages are scattered along river basins.
Neighbouring municipalities Yamaguchi Prefecture •
Hikari •
Hirao •
Iwakuni •
Kaminoseki •
Suō-Ōshima •
Tabuse Climate Yanai has a
humid subtropical climate (
Köppen climate classification Cfa) with hot summers and cool winters. Precipitation is significant throughout the year, but is much higher in summer than in winter. The average annual temperature in Yanai is . The average annual rainfall is with July as the wettest month. The temperatures are highest on average in August, at around , and lowest in January, at around . The highest temperature ever recorded in Yanai was on 18 August 2010; the coldest temperature ever recorded was on 27 February 1981. {{Weather box
Demographics Per Japanese census data, the population of Yanai in 2020 is 30,799 people. Yanai has been conducting censuses since 1920. ==History==