This report describes the typical weather at the Florida Keys Marathon Airport (Marathon, Florida, United States) weather station over the course of an average May. It is based on the historical records from 1998 to 2012. Earlier records are either unavailable or unreliable.
Marathon, Florida has a tropical savanna climate with dry winters. The area within 25 mi of this station is covered by oceans and seas (100%).
The month of May is characterized by gradually rising daily high temperatures, with daily highs around 86°F throughout the month, exceeding 90°F or dropping below 81°F only one day in ten.
Over the course of May, the length of the day is essentially constant. The shortest day of the month is May 1 with 13:05 hours of daylight; the longest day is May 31 with 13:34 hours of daylight.
The earliest sunrise is at 6:35am on May 29; the latest sunset is at 8:09pm on May 31; the latest sunrise is at 6:49am on May 1; the earliest sunset is at 7:54pm on May 1.
Daylight saving time is observed in 2012 but it neither starts nor ends in May, so the entire month is in daylight time.
The median cloud cover is 13% (mostly clear) and does not vary substantially over the course of the month.
On May 16, a representative day, the sky is clear or mostly clear 71% of the time, partly cloudy 10% of the time, and mostly cloudy or overcast 17% of the time.
The probability that precipitation will be observed at this location varies throughout the month. Precipitation is most likely around May 31, occurring in 38% of days. Precipitation is least likely around May 1, occurring in 22% of days.
Throughout May, the most common forms of precipitation are thunderstorms, light rain, heavy rain, and moderate rain.
Thunderstorms are the most severe precipitation observed during 43% of those days with precipitation. They are most likely around May 31, when it is observed during 19% of all days.
Light rain is the most severe precipitation observed during 27% of those days with precipitation. It is most likely around May 27, when it is observed during 9% of all days.
Heavy rain is the most severe precipitation observed during 15% of those days with precipitation. It is most likely around May 28, when it is observed during 5% of all days.
Moderate rain is the most severe precipitation observed during 15% of those days with precipitation. It is most likely around May 29, when it is observed during 5% of all days.
Either snow is exceptionally unlikely to fall at this location in May or this station does not reliably report precipitation types.
The relative humidity typically ranges from 57% (mildly humid) to 83% (humid) over the course of a typical May, rarely dropping below 46% (comfortable), or exceeding 93% (very humid).
The air is driest around May 1, at which time the relative humidity drops below 63% (mildly humid) three days out of four; it is most humid around May 28, rising above 79% (humid) three days out of four.
Dew point is often a better measure of how comfortable a person will find the weather than relative humidity because it more directly relates to whether perspiration will evaporate from the skin, thereby cooling the body. Lower dew points feel drier and higher dew points feel more humid.
Over the course of a typical May, the dew point typically varies from 65°F (mildy humid) to 75°F (very muggy) and is rarely below 57°F (comfortable) or above 77°F (oppressive).
Over the course of May typical wind speeds vary from 2 mph to 12 mph (light air to moderate breeze), rarely exceeding 17 mph (moderate breeze).
The highest average wind speed of 9 mph (gentle breeze) occurs around May 1, at which time the average daily maximum wind speed is 12 mph (moderate breeze).
The lowest average wind speed of 7 mph (light breeze) occurs around May 28, at which time the average daily maximum wind speed is 11 mph (gentle breeze).