Weather

Month Average High Air Temp Average Low Air Temp Average Water Temp Average Rainfall (inches)
January 74 65 69 2.0
February 75 66 70 1.8
March 78 69 75 1.7
April 81 72 79 1.8
May 85 76 83 3.5
June 87 79 86 5.1
July 89 80 87 3.6
August 89 79 87 5.0
September 88 79 86 5.9
October 84 76 82 4.4
November 80 71 76 2.9
December 76 67 72 2.0
This data is technically for Key West, but is close enough.
The actual air temperatures may run 10 degrees above the “average”.  The overnight low temperatures in
December and January can approach 50 – 55.
Water temperatures are very stable and usually vary less than a degree or two over the course of a day.  Thermoclines are rare but occasionally present in the winter and spring.  SUMMERTIME “FEELS LIKE” TEMPERATURES WILL FREQUENTLY APPROACH THE 110º – 115º RANGE.  Our humidity is generally above 70%.  Use the high temperature from the chart above for the month you are attending PLUS 70% or higher humidity to find the heat index (or feels like temperature) in the chart below.

Heat Index Chart

The Heat Index is the temperature the body feels when heat and humidity are combined. The chart below shows the Heat Index that corresponds to the actual air temperature and relative humidity. This chart is based upon shady, light wind conditions. Exposure to direct sunlight can increase the Heat Index by up to 15 degrees Fahrenheit.

 

Relative Humidity (%)
40 45 50 55 60 65 70 75 80 85 90 95 100
110 136
108 130 137
106 124 130 137
104 119 124 131 137
102 114 119 124 130 137
100 109 114 118 124 129 136
98 105 109 113 117 123 128 134
96 101 104 108 112 116 121 126 132
94 97 100 102 106 110 114 119 124 129 135
92 94 96 99 101 105 108 112 116 121 126 131
90 91 93 95 97 100 103 106 109 113 117 122 127 132
88 88 89 91 93 95 98 100 103 106 110 113 117 121
86 85 87 88 89 91 93 95 97 100 102 105 108 112
84 83 84 85 86 88 89 90 92 94 96 98 100 103
82 81 82 83 84 84 85 86 88 89 90 91 93 95
80 80 80 81 81 82 82 83 84 84 85 86 86 87
With Prolonged Exposure and/or Physical Activity:
Caution:
Fatigue possible
Extreme Caution:
Sunstroke, muscle cramps, and/or heat exhaustion possible
Danger:
Sunstroke, muscle cramps, and/or heat exhaustion likely
Extreme Danger:
Heat Stroke or Sunstroke likely

Approximately 400 people die each year from exposure to heat, according to the Centers for Disease Control and Prevention. Our bodies dissipate heat by varying the rate and depth of blood circulation, by losing water through the skin and sweat glands, and as a last resort, by panting, when blood is heated above 98.6 degrees Fahrenheit.

Sweating cools the body through evaporation. However, high relative humidity retards evaporation, robbing the body of its ability to cool itself. When heat gain exceeds the level the body can remove, body temperature begins to rise, and heat-related illnesses and disorders may develop.

If you must be out in the heat:

 

  • Limit your outdoor activity to morning and evening hours.
  • Cut down on exercise. If you must exercise, drink two to four glasses of cool, nonalcoholic fluids each hour. A sports beverage can replace the salt and minerals you lose in sweat.
    Warning: If you are on a low-salt diet, talk with your doctor before drinking a sports beverage.
  • Try to rest often in shady areas.
  • Protect yourself from the sun by wearing a wide-brimmed hat (also keeps you cooler) and sunglasses and by putting on sunscreen of SPF 15 or higher (the most effective products say “broad spectrum” or “UVA/UVB protection” on their labels).

Provided by the National Weather Service

 

WHILE WETSUITS ARE GENERALLY NOT REQUIRED, THE FLORIDA SEA BASE RENTS 3mm ONE PIECE, LONG SLEEVED, LONG LEGGED WETSUITS FOR $25 PER WEEK TO SCUBA CREWS IF YOU THINK THE WATER IS TOO COLD.  SCUBA CREWS ARE WELCOME TO BRING A WETSUIT FROM HOME IF THEY WANT.  WE DO NOT ENCOURAGE WETSUITS FOR THE SAILING CREWS BECAUSE (1) YOUR EXPOSURE TIME WHILE SNORKELING IS RATHER LIMITED (2) THERE IS NO PLACE TO STORE THE WET WETSUITS ABOARD THE VESSELS (3) IF THE WATER IS TOO COLD YOU CAN FISH AND SAIL.

For current weather conditions and forecasts click on the Weather Underground sticker near the top left corner of the page.

The link to the National Weather Service Marine Forecast for the Florida Keys is
http://forecast.weather.gov/MapClick.php?map.x=296&map.y=155&site=key&zmx=1&zmy=1


Tropical Weather Tracker