limestone is from 15 to 25 million years old. Climate The county has a Köppen climate classification of Cf with a year-round distribution of rainfall. This means a humid subtropical climate with hot, humid summers. There are distinct wet and dry seasons. The dry lasts from December through May, the wet from June through November. During the dry season, periods of drought often occur, and can lead to a persistent and high wild land fire threat. In numerous instances these fires have caused property damage. Several fires in 2008 forced the evacuation of Bayside High School, in the town of Palm Bay. In that particular event, 162 homes were damaged. January is the coldest month, with an average low of and an average high . The warmest months are July and August with average highs of and average lows of . The driest month is April with of rainfall; the wettest is September, with . Offshore ocean temperatures have averaged: January – , February – , March – and April – . In federal maps printed before 2012, nearly half of Brevard was classified as prone to flooding. Most of this was in the relatively undeveloped low-lying areas, west of Interstate 95, on the banks of the St. Johns River. About 18,900 homes out of 164,000 single-family homes were in that area. Florida is a large subtropical state that is regularly affected by hurricanes. Although Brevard County is located along Florida's eastern peninsula, because of associated weather patterns, it is less frequently hit by direct hurricane landfalls than are portions of the Panhandle or South Florida. There are two predominant reasons for this. First, westward-moving tropical systems often reach an atmospheric ridge weakness in the Bermuda High by the time they approach Florida at a latitude as northerly as Brevard County. Combined with frontal systems that exit the United States' East Coast, many of these tropical systems are steered northwest and eventually curve northward offshore along Florida's East Central Coast. A second reason is that hurricanes making landfall along the Florida peninsula Gulf Coast often weaken to a tropical storm by the time they move northeast and reach Brevard County. (2004's Charley was an exception). No major hurricane, defined as category 3 or higher, has struck Brevard since 1850, the beginning of recorded climate. Although residents may refer to past storms as "hurricanes", by the time they strike the county,