Marathon, Florida climate: Normal weather by month, frost dates and records
Marathon's normal year runs from 64°F January nights to 92°F August afternoons, with 39.7 inches of precipitation a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 26.0°C, January lows of 18°C, August highs of 33°C, 1,009 mm of precipitation a year.
- NOAA stationMarathon Airport
- Station IDUSW00012896
- Location24.73°N 81.05°W
- Elevation8 ft (2 m)
- From the center2 miles
- Population10,039
On October 23, the normal high in Marathon is 85°F and the normal low 75°F, and the chance of measurable rain or snow is 34%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Marathon.
- Jan 76° 64°
- Feb 78° 66°
- Mar 81° 69°
- Apr 84° 73°
- May 88° 76°
- Jun 90° 79°
- Jul 91° 79°
- Aug 92° 80°
- Sep 90° 78°
- Oct 86° 76°
- Nov 81° 71°
- Dec 78° 68°
Each month: normal high (large) and low, °F. Fill: the month's normal mean, colder blue to hotter red.
What is the weather like in Marathon each month?
August is the warmest month, with normal highs of 92°F; January the coldest, with normal lows of 64°F. The most precipitation falls in September (6.37 in), the least in March (1.33 in).
| Month | High | Low | Mean | Precip. | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|
| January | 76°F | 64°F | 70.0°F | 1.64 | 8 | <1 | <1 | 10 h 50 min |
| February | 78°F | 66°F | 72.3°F | 1.70 | 6 | <1 | <1 | 11 h 20 min |
| March | 81°F | 69°F | 74.6°F | 1.33 | 6 | <1 | <1 | 12 h |
| April | 84°F | 73°F | 78.3°F | 2.11 | 5 | 2 | <1 | 12 h 40 min |
| May | 88°F | 76°F | 81.7°F | 3.36 | 8 | 7 | <1 | 13 h 20 min |
| June | 90°F | 79°F | 84.4°F | 4.23 | 10 | 19 | <1 | 13 h 40 min |
| July | 91°F | 79°F | 85.2°F | 3.77 | 13 | 26 | <1 | 13 h 30 min |
| August | 92°F | 80°F | 85.6°F | 5.32 | 14 | 27 | <1 | 13 h |
| September | 90°F | 78°F | 84.2°F | 6.37 | 15 | 19 | <1 | 12 h 20 min |
| October | 86°F | 76°F | 81.0°F | 5.90 | 12 | 5 | <1 | 11 h 40 min |
| November | 81°F | 71°F | 76.0°F | 1.79 | 7 | <1 | <1 | 11 h |
| December | 78°F | 68°F | 72.7°F | 2.20 | 8 | <1 | <1 | 10 h 40 min |
| Year (annual) | 85°F | 73°F | 78.8°F | 39.72 | 112 | 105 | <1 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. |
|---|---|---|---|---|
| January | 24°C | 18°C | 21.1°C | 42 mm |
| February | 26°C | 19°C | 22.4°C | 43 mm |
| March | 27°C | 20°C | 23.7°C | 34 mm |
| April | 29°C | 23°C | 25.7°C | 54 mm |
| May | 31°C | 24°C | 27.6°C | 85 mm |
| June | 32°C | 26°C | 29.1°C | 107 mm |
| July | 33°C | 26°C | 29.6°C | 96 mm |
| August | 33°C | 27°C | 29.8°C | 135 mm |
| September | 32°C | 26°C | 29.0°C | 162 mm |
| October | 30°C | 24°C | 27.2°C | 150 mm |
| November | 27°C | 22°C | 24.4°C | 45 mm |
| December | 26°C | 20°C | 22.6°C | 56 mm |
Source: NOAA NCEI 1991-2020 monthly normals, station USW00012896; annual normals. Wet days: 0.01 inch or more; 90°F days and freezing nights: NOAA's day counts. Daylight: sunrise to sunset on the 15th, computed from the latitude.
When is the best weather to visit Marathon?
Normal highs sit between 65°F and 85°F in January, February, March, April, November and December. Of those, April has the fewest days with rain (5).
That is a measurement, not a recommendation: it counts the months whose normal afternoon high sits between 65°F and 85°F, where a light layer is enough by day.
Source: NOAA NCEI 1991-2020 monthly normals, station USW00012896.
How hot and how cold does it get in Marathon?
In a normal year in Marathon, 105 days a year reach 90°F, nights almost never fall to freezing and 112 days bring measurable precipitation.
- Days at 90°F or more
- 105a normal year
- Days at 100°F or more
- fewer than 1a normal year
- Nights at 32°F or colder
- fewer than 1a normal year
- Days that stay below freezing
- fewer than 1high of 32°F or less
- Days with 0.01 inch of precipitation
- 112a normal year
The highest temperature in Marathon's official record (kept by the National Weather Service since 1950) is 99°F, on July 15, 1987; the lowest is 37°F, on December 25, 1989.
The wettest calendar year on that record is 1959, with 70.09 in.
Source: NOAA NCEI 1991-2020 annual normals, station USW00012896; records: ACIS (NOAA Regional Climate Centers), NWS threaded record MTHthr. Records use complete months only; a month missing more than three days is left out.
How sunny is Marathon?
Over a year 85% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Marathon, 5.4 kWh per square metre a day. April is the sunniest month (90%) and January the cloudiest (81%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 81% | 3.9 |
| February | 85% | 4.8 |
| March | 89% | 5.9 |
| April | 90% | 6.6 |
| May | 88% | 6.7 |
| June | 83% | 6.3 |
| July | 85% | 6.3 |
| August | 85% | 6.1 |
| September | 82% | 5.4 |
| October | 84% | 4.8 |
| November | 84% | 4.1 |
| December | 83% | 3.6 |
Source: NASA POWER solar climatology, 2001-2020 (CERES SYN1deg). Satellite-based, for the 1-degree cell (about 100 km across) around the station, so it describes the area rather than the airport.
How much heating and cooling does Marathon need?
A normal year in Marathon brings 71 heating degree days, 99% fewer than the median U.S. place (5,373), and 5,128 cooling degree days, 5.7 times the median (908). No month reaches 300 heating degree days. For gardens and crops, NOAA counts 10,532 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 33 | 188 |
| February | 15 | 218 |
| March | 5 | 302 |
| April | 0 | 399 |
| May | 0 | 516 |
| June | 0 | 582 |
| July | 0 | 625 |
| August | 0 | 640 |
| September | 0 | 575 |
| October | 0 | 496 |
| November | 1 | 331 |
| December | 17 | 256 |
| Year (annual) | 71 | 5,128 |
Source: NOAA NCEI 1991-2020 monthly normals, station USW00012896. A degree day is one degree of a day's mean temperature below 65°F (heating) or above it (cooling); utilities use them to estimate energy use.
Has Marathon been warmer than normal lately?
2025 averaged 78.9°F, 0.1°F above the 1991-2020 normal of 78.8°F. 5 of the 5 complete years since 2021 ran warmer than the normal.
| Year | Mean | Against normal | Precip. |
|---|---|---|---|
| 2021 | 78.9°F | +0.1°F | 34.49 |
| 2022 | 80.5°F | +1.7°F | 34.73 |
| 2023 | 81.4°F | +2.6°F | 52.56 |
| 2024 | 79.6°F | +0.8°F | 49.38 |
| 2025 | 78.9°F | +0.1°F | 38.38 |
Source: observed years: ACIS, station USW00012896. A year counts only with all twelve months complete.
How does Marathon's climate compare?
Marathon is warmer than 104 of the other 105 places with their own NOAA record in Florida, and wetter than 0. Across the 7,247 U.S. stations with normals, its annual mean of 78.8°F is warmer than 100%.
In the Köppen classification computed from these normals, Marathon is Aw: tropical savanna. What the classes mean.
Places with the most similar year elsewhere
Measured month by month on the normal high, low and precipitation, among places of 20,000 or more people in other states:
Source: NOAA NCEI 1991-2020 normals for every station PlainClimate covers. Similarity: the root-mean-square difference of the 36 monthly figures, precipitation weighted so an inch counts like 6°F.
Which places near Marathon share this climate record?
Key Colony Beach has no NOAA station with 1991-2020 normals of its own, and this station is the nearest full record. A place's own climate can differ from these figures, by several degrees where it sits much higher or lower than the station, nearer the coast, or inside a large city's heat; for the larger places the next nearest records are named with their yearly mean, so the spread around them is visible, and places of 50,000 or more have their own page with NOAA's gridded normals.
- Key Colony Beach, FL749 people · 2 mi E
Source: Census Bureau 2024 Gazetteer (place centers) and Vintage 2024 population estimates. Distance and direction from the station to each place's center.
Questions about Marathon's climate
What is the coldest month in Marathon?
January, with a normal high of 76°F and a normal low of 64°F. The warmest is August (92°F by day, 80°F at night).
What is the rainiest month in Marathon?
September, with 6.37 in of precipitation in a normal year; the driest is March with 1.33 in.
What plant hardiness zone is Marathon in?
The USDA's 2023 map puts Marathon in zone 11b in ZIP code 33050. By the same method at Marathon's NOAA station, the coldest night of a typical year reaches 48°F (22 years, 1991-2020): zone 11b.
Nearby and next
- Florida climateThe statewide normals and every place in the state
- Curry Hammock State Park, FL4 miles from this station, 77.8°F a year
- Duck Key, FL9 miles from this station, 77.5°F a year
- Bahia Honda State Park, FL15 miles from this station, 77.6°F a year
- Islamorada, FL29 miles from this station, 77.9°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made