BISCAYNE Biscayne National Monument A Proposal

"Subtropical" aptly describes the warm, mild climate of this part of the United States. The Gulf Stream, a few miles off shore, keeps the waters of Biscayne Bay and the Florida Keys at fairly even temperatures year round; trade winds warm the air in winter and cool it in summer.

In Dade County, mean maximum temperatures range from about 77 degrees in January to about 90 degrees in August. Mean minimum temperatures range from about 54 degrees in February to near 72 in July and August. Killing frosts are infrequent. Temperatures of 32 degrees or less occur about every other year at Homestead and much less frequently near the ocean. From June through October, the relatively high humidity averages from 60 to almost 90 percent; in the dry winter season, however, the comfort index improves 5 to 10%.

Average annual rainfall runs between 50 and 60 inches. The rainy season occurs in summer and early fall, most rain coming in September and October, while the winter months, November through March, are usually quite dry. Over 60 percent of the days are classified either as clear or partly cloudy, with most of the clear days occurring during the winter months.

Astronomical tides along the coastline of the upper Florida Keys ebb and flow twice during each lunar day. Mean tide ranges vary from about 2 feet at Sands Key to about .2 foot in lower Barnes Sound, and mean high tide in the same area varies from about 1 foot to about .1 foot. Although maximum hurricane tide of 16 feet may occur, surf and heavy wave action are almost entirely absent along the oceanfront of the area proposed for National Monument status.

Occasionally this section of the country is struck by hurricanes, some of which cause heavy damage. Especially severe hurricanes occurred in September 1926, November 1935, September 1945, October 1950, and September 1960. Hurricanes occur most frequently in September and October.