It is rare for there to be snow in Florida. Snow rarely occurs because freezing temperatures in Florida are generally caused by the cold and dry winds of anticyclones. Frost is more common than snow, requiring temperatures of 45°F (7°C) or less at 2 metres (7 ft) above sea level, a cloudless sky, and a relative humidity of 65% or more. Generally, for snow to occur, the polar jet stream must move southward through Texas and into the Gulf of Mexico, with a stalled cold front across the southern portion of the state curving northeastward to combine freezing air into the frontal clouds. Much of the known information on snow in Florida prior to 1900 is from weather climatology provided by the Jacksonville National Weather Service; for this reason, information for other locations is sparse. The first white Christmas in Jacksonville's history resulted from a snowfall that occurred on December 23, 1989 (pictured). (Full list...)