This report describes the typical weather at the St. Augustine Airport (St. Augustine, Florida, United States) weather station over the course of an average December. It is based on the historical records from 1997 to 2012. Earlier records are either unavailable or unreliable.
St. Augustine, Florida has a warm humid temperate climate with hot summers and no dry season. The area within 25 mi of this station is covered by oceans and seas (46%), forests (39%), croplands (9%), and lakes and rivers (5%).
The month of December is characterized by falling daily high temperatures, with daily highs ranging from 69°F to 65°F over the course of the month, exceeding 78°F or dropping below 53°F only one day in ten.
Over the course of December, the length of the day is essentially constant. The shortest day of the month is December 26 with 10:13 hours of daylight; the longest day is December 1 with 10:22 hours of daylight.
The earliest sunrise is at 7:04am on December 1; the latest sunset is at 5:37pm on December 31; the latest sunrise is at 7:21am on December 30; the earliest sunset is at 5:25pm on December 3.
Daylight savings time is observed in 2012 but it neither starts nor ends in December, so the entire month is in standard time.
The median cloud cover is 22% (mostly clear) and does not vary substantially over the course of the month.
On December 16, a representative day, the sky is clear or mostly clear 59% of the time, partly cloudy 6% of the time, and mostly cloudy or overcast 32% of the time.
The average probability that some form of precipitation will be observed in a given day is 9%, with little variation over the course of the month.
Throughout December, the most common forms of precipitation are light rain, thunderstorms, and moderate rain.
Light rain is the most severe precipitation observed during 43% of those days with precipitation. It is most likely around December 24, when it is observed during 4% of all days.
Thunderstorms are the most severe precipitation observed during 29% of those days with precipitation. They are most likely around December 24, when it is observed during 3% of all days.
Moderate rain is the most severe precipitation observed during 20% of those days with precipitation. It is most likely around December 31, when it is observed during 2% of all days.
Either snow is exceptionally unlikely to fall at this location in December or this station does not reliably report precipitation types.
The relative humidity typically ranges from 53% (mildly humid) to 91% (very humid) over the course of a typical December, rarely dropping below 33% (comfortable) and reaching as high as 100% (very humid).
The air is driest around December 30, at which time the relative humidity drops below 65% (mildly humid) three days out of four; it is most humid around December 2, rising above 88% (very 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 December, the dew point typically varies from 39°F (dry) to 59°F (comfortable) and is rarely below 22°F (dry) or above 68°F (muggy).
The time of the month between December 1 and December 31 is the most comfortable, with dew points that are neither too dry nor too muggy.
Over the course of December typical wind speeds vary from 0 mph to 14 mph (calm to moderate breeze), rarely exceeding 19 mph (fresh breeze).
The highest average wind speed of 8 mph (gentle breeze) occurs around December 16, at which time the average daily maximum wind speed is 14 mph (moderate breeze).
The lowest average wind speed of 7 mph (light breeze) occurs around December 28, at which time the average daily maximum wind speed is 14 mph (moderate breeze).