Temperature in the Florida Keys in December

Wendy K. Leigh, Leaf Group

Savvy tropical travelers know that December is a prime month for traveling the Overseas Highway toward Key West, the Southernmost tip of the continental United States. The small island of Key West has a big reputation, and most of it centers around the balmy weather. Snowbirds flock to the land of Hemingway, margaritas and authentic Cuban cuisine every winter, as well as to the dozens of other keys scattered along the 110-mile strip of highway jutting into the Gulf of Mexico on one side and the Atlantic Ocean on the other.

The Lowdown on High Temps

When the rest of America chills down, the Florida Keys chill out. With the hot and humid summer months behind them, residents prepare for the onslaught of winter visitors escaping the cold weather in their home states. Air temperatures in the Keys average highs of 76 degrees Fahrenheit in December, a considerable drop from the damp heat and near 90-degree averages from June through September. Average low air temps in December bottom out at just 67 degrees.

Humidity Plays a Part

The level of humidity in the Keys can make heat seem more oppressive and uncomfortable. It is still relatively high in December, but much more tolerable than the moisture-laden air of the preceding months. The relative humidity in the city of Marathon, which is about halfway through the Florida Keys, generally ranges from 62 to 88 percent over the span of days in a typical December. Record highs have reached 98 percent, but that is a rare occurrence in the winter months. The air usually dries out more toward the end of the month.

Aquatic Temps

The Florida Keys are all about water; you gaze at it, snorkel in it, float on it and drink a whole lot of it after cycling, surfing and fishing all day in the sun. That means that water temperatures are an important component of a trip to the Keys. From highs in the upper 80s Fahrenheit in the summer months, water temperatures drop to an average of 72 degrees in December. Remember that the Florida Keys lie within two separate bodies of water that merge at the tip of Key West, so water temperatures will vary slightly depending on whether you are in the Gulf of Mexico or the Atlantic Ocean. Swimming pools heated only by solar energy will naturally be cooler in December than in August.

More to Consider

When anticipating the heat to expect when visiting the Florida Keys, there are a few factors to consider. Cooling ocean breezes make the warm air and humidity more tolerable, particularly if you stay close to the coastline. When the sun sets, things generally cool down to a more comfortable level. Even during the hottest parts of the day, you will not feel the heat as intensely as in urban areas, due to the lack of freeways and tall buildings radiating the heat from all directions.

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