Florida has experienced 12 major freezes. This includes four "impact" freezes, sufficiently severe to kill entire groves of citrus trees, resulting in a noticeable economic effect on citrus growers, prompting them to shift groves further southward. These impact freezes are indicated by asterisks in the following: Great Freeze of 1894-5*, February 13–14, 1899, February 2–6, 1917, December 12–13, 1934, January 1940, December 12–13, 1957, December 12–13, 1962*, January 18–20, 1977, January 12–14, 1981, December 24–25, 1983*, January 20–22, 1985, and December 22–26, 1989*.