Michigan contains five American Viticultural Areas (AVAs), regions whose wines share similar and distinct characteristics: Fennville, Lake Michigan Shore, Leelanau Peninsula, Old Mission Peninsula, and Tip of the Mitt. All five regions are located in proximity to Lake Michigan, and almost all of Michigan's wine grapes are grown within 25 miles (40 km) of the lake. The lake effect provides a favorable microclimate compared to interior regions of the state. The northern wine regions have a 145-day growing season while the southern ones have a 160-day season.