Marathon Weather

Average monthly temperature and rainfall in Marathon

Dolphin Encounter in Marathon, FL
••• Becky DiCello of Parker, Colorado greets a resident dolphin at the Dolphin Research Center in Marathon, FL. © Photographer, Debbie Speak/Getty Images

Environment-friendly attractions are what draws visitors to Marathon, located midway between Key Largo and Key West in the Florida Keys. Of course, with an overall average high temperature of 84° and an average low of 66°, it might just be the weather that makes them want to stay.

Packing for a vacation in Marthon is pretty simple since most of the attractions are outdoors. Bring your bathing suit to swim with the dolphins; and, of course, you will also need resort casual clothing for dining out, but cool, casual and comfortable is the dress code.

On average, Marathon's warmest month is July and January is the average coolest month. The highest recorded temperature in Marathon was a sweltering 104° in 1998 and the lowest recorded temperature was a very chilly 25° in 1989. The maximum average rainfall usually falls in August. The Florida Keys are not often affected by hurricanes, but do know that the unpredictable storms are a possibility during the Atlantic hurricane season which runs from June 1 through November 30.

Average temperatures, rainfall and sea temperatures for Marathon:

January

  • Average High: 77° F
  • Average Low: 56° F
  • Average Precipitation: 1.94 inches
  • Average Sea Temperature: 72.4° F

February

  • Average High Temperature: 78° F
  • Average Low Temperature: 57° F
  • Average Precipitation: 1.63 inches
  • Average Sea Temperature: 72.2° F

March

  • Average High Temperature: 80° F
  • Average Low Temperature: 60° F
  • Average Precipitation: 1.84 inches
  • Average Sea Temperature: 74.1° F

    April

    • Average High Temperature: 83° F
    • Average Low Temperature: 64° F
    • Average Precipitation: 2.06 inches
    • Average Sea Temperature: 78.1° F

    May

    • Average High Temperature: 87° F
    • Average Low Temperature: 69° F
    • Average Precipitation: 5.06 inches
    • Average Sea Temperature: 80.9° F

    June

    • Average High Temperature: 89° F
    • Average Low Temperature: 73° F
    • Average Precipitation: 7.25 inches
    • Average Sea Temperature: 83.4° F

    July

    • Average High Temperature: 90° F
    • Average Low Temperature: 74° F
    • Average Precipitation: 4.73 inches
    • Average Sea Temperature: 85.4° F

    August

    • Average High Temperature: 90° F
    • Average Low Temperature: 74° F
    • Average Precipitation: 7.43 inches
    • Average Sea Temperature: 86.8° F

    September

    • Average High Temperature: 89° F
    • Average Low Temperature: 74° F
    • Average Precipitation: 7.20 inches
    • Average Sea Temperature: 85.4° F

    October

    • Average High Temperature: 87° F
    • Average Low Temperature: 69° F
    • Average Precipitation: 4.26 inches
    • Average Sea Temperature: 82.8° F

    November

    • Average High Temperature: 83° F
    • Average Low Temperature: 64° F
    • Average Precipitation: 2.46 inches
    • Average Sea Temperature: 78.6° F

    December

    • Average High Temperature: 79° F
    • Average Low Temperature: 59° F
    • Average Precipitation: 1.57 inches
    • Average Sea Temperature: 75.2° F

    Visit weather.com for current weather conditions, 5- or 10-day forecast and more.

    If you're planning a Florida vacation or getaway, find out more about weather, events and crowd levels from our month-by-month guides.