Marathon, Florida Keys weather in August
Temperature, sea and sunshine in August: long-term averages from 30 years of weather data, not a forecast.
Holiday weather in August
Excellent
Best time to visit: March – May, July, November – December
What is the weather like in Marathon, Florida Keys in August?
In August, Marathon, Florida Keys is hot: daytime highs average 29 °C, and even at night it stays warm at around 28 °C. The sea averages 30.1 °C – almost as warm as a bath. The sun shines for around 8 hours a day. It rains often – on about 16 days, adding up to 112 mm. The air is often humid and muggy. All in all, August is an excellent month for a holiday in Marathon, Florida Keys.
August compared
How the weather changes from July to September. Tap a month to open it.
| JulyJul | AugustAug | SeptemberSep | |
|---|---|---|---|
| Score | 85 | 81 | 75 |
| Day | 29° | 29° | 29° |
| Night | 27° | 28° | 27° |
| Sea | 30° | 30° | 30° |
| Sun | 9 h | 8 h | 7 h |
| Rain days | 14 | 16 | 17 |
More details for August
- Daylight
- 13 h 2 min06:58 – 20:00
- UV index
- 12 · extremeclear sky, noon (estimate)All months
- Muggy days
- 31 daysdew point 18 °C or moreAll months
- Wind
- 23 km/haverage daily peakAll months
- Cloud cover
- 61 %on averageAll months
- Hot days
- 2 days30 °C or moreAll months
- Time zone
- UTC−4America/New_York
How the score comes together
- Temperatureweight 35 %100 %
- Seaweight 25 %100 %
- Sunshineweight 20 %88 %
- Few rainy daysweight 20 %16 %
Each factor is rated from 0 to 100 % and weighted for the travel style “Sun, sea & sand”.
What to pack in August
- Swimwear
- Sunscreen
- Sunglasses & sun hat
- Light, breathable clothes
- Insect repellent
- Rain jacket or umbrella
Marathon, Florida Keys in August: quick answers
Is Marathon, Florida Keys hot in August?
Yes. In August, Marathon, Florida Keys is hot: daytime highs average 29 °C and nights stay around 28 °C. On about 2 days the thermometer climbs to 30 °C or more.
Can you swim in Marathon, Florida Keys in August?
Yes. In August the sea averages 30.1 °C – almost as warm as a bath.
Does it rain much in Marathon, Florida Keys in August?
It rains often – on about 16 days, adding up to 112 mm.
Marathon, Florida Keys month by month
The whole year in Marathon, Florida KeysAll destinations: USAFlorida weather in AugustWhere to go in AugustSea temperature in August
Climate averages 1996–2025, not a forecast. Data: Copernicus ERA5 / ERA5-Land via Open-Meteo.com (CC BY 4.0), NOAA OISST, WMO 1991–2020 (NOAA NCEI), GeoNames (CC BY 4.0). Sources & licences