Average Weather In December For St. Croix, US Virgin Islands

Location

This report describes the typical weather at the Henry E. Rohlsen Airport (St. Croix, US Virgin Islands) weather station over the course of an average December. It is based on the historical records from 1991 to 2012. Earlier records are either unavailable or unreliable.

St. Croix has a tropical savanna climate with dry winters. The area within 25 mi of this station is covered by oceans and seas (96%) and forests (2%).

Temperature

The month of December is characterized by essentially constant daily high temperatures, with daily highs around 84°F throughout the month, exceeding 87°F or dropping below 81°F only one day in ten.

Daily High and Low Temperature in December

The daily average low (blue) and high (red) temperature with percentile bands (inner band from 25th to 75th percentile, outer band from 10th to 90th percentile).
Daily low temperatures are around 74°F, falling below 70°F or exceeding 78°F only one day in ten.

Fraction of Time Spent in Various Temperature Bands in December

The average fraction of time spent in various temperature bands: frigid (below 15°F), freezing (15°F to 32°F), cold (32°F to 50°F), cool (50°F to 65°F), comfortable (65°F to 75°F), warm (75°F to 85°F), hot (85°F to 100°F) and sweltering (above 100°F).

Sun

Over the course of December, the length of the day is essentially constant. The shortest day of the month is December 27 with 11:04 hours of daylight; the longest day is December 1 with 11:10 hours of daylight.

Daily Hours of Daylight and Twilight in December

The number of hours during which the Sun is visible (black line), with various degrees of daylight, twilight, and night, indicated by the color bands. From bottom (most yellow) to top (most gray): full daylight, solar twilight (Sun is visible but less than 6° from the horizon), civil twilight (Sun is not visible but is less than 6° below the horizon), nautical twilight (Sun is between 6° and 12° below the horizon), astronomical twilight (Sun is between 12° and 18° below the horizon), and full night.

The earliest sunrise is at 6:34am on December 1; the latest sunset is at 5:55pm on December 31; the latest sunrise is at 6:50am on December 31; the earliest sunset is at 5:43pm on December 2.

Daylight saving time (DST) is not observed in 2012.

Daily Sunrise & Sunset with Twilight in December

The solar day over the course of the year 2012 . From bottom to top, the black lines are the previous solar midnight, sunrise, solar noon, sunset, and the next solar midnight. The day, twilights (solar, civil, nautical, and astronomical), and night are indicated by the color bands from yellow to gray.

Clouds

The median cloud cover is 42% (partly cloudy) and does not vary substantially over the course of the month.

Median Cloud Cover in December

The median daily cloud cover (black line) with percentile bands (inner band from 40th to 60th percentile, outer band from 25th to 75th percentile).

On December 16, a representative day, the sky is clear or mostly clear 38% of the time, partly cloudy 24% of the time, and mostly cloudy or overcast 21% of the time.

Cloud Cover Types in December

The fraction of time spent in each of the five sky cover categories. From top (most blue) to bottom (most gray), the categories are clear, mostly clear, partly cloudy, mostly cloudy, and overcast. Pink indicates missing data. Outside of the United States clear skies are often reported ambiguously, leading them to be lumped in with the missing data.

Precipitation

The probability that precipitation will be observed at this location varies throughout the month. Precipitation is most likely around December 1, occurring in 45% of days. Precipitation is least likely around December 17, occurring in 41% of days.

Probability of Precipitation at Some Point in the Day in December

The fraction of days in which various types of precipitation are observed. If more than one type of precipitation is reported in a given day, the more severe precipitation is counted. For example, if light rain is observed in the same day as a thunderstorm, that day counts towards the thunderstorm totals. The order of severity is from the top down in this graph, with the most severe at the bottom.

Throughout December, the most common forms of precipitation are light rain, moderate rain, and heavy rain.

Light rain is the most severe precipitation observed during 55% of those days with precipitation. It is most likely around December 23, when it is observed during 24% of all days.

Moderate rain is the most severe precipitation observed during 27% of those days with precipitation. It is most likely around December 1, when it is observed during 12% of all days.

Heavy rain is the most severe precipitation observed during 14% of those days with precipitation. It is most likely around December 1, when it is observed during 7% of all days.

Types of Precipitation Throughout December

Relative frequency of various types of precipitation over the course of a typical December.

Snow

Either snow is exceptionally unlikely to fall at this location in December or this station does not reliably report precipitation types.

Humidity

The relative humidity typically ranges from 63% (mildly humid) to 89% (very humid) over the course of a typical December, rarely dropping below 55% (mildly humid) and reaching as high as 97% (very humid).

The air is driest around December 24, at which time the relative humidity drops below 67% (mildly humid) three days out of four; it is most humid around December 11, rising above 85% (humid) three days out of four.

Relative Humidity in December

The average daily high (blue) and low (brown) relative humidity with percentile bands (inner bands from 25th to 75th percentile, outer bands from 10th to 90th percentile).

Dew Point

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 67°F (muggy) to 73°F (very muggy) and is rarely below 64°F (mildy humid) or above 76°F (oppressive).

Dew Point in December

The daily average low (blue) and high (red) dew point with percentile bands (inner band from 25th to 75th percentile, outer band from 10th to 90th percentile).

Wind

Over the course of December typical wind speeds vary from 6 mph to 17 mph (light breeze to moderate breeze), rarely exceeding 22 mph (fresh breeze).

The highest average wind speed of 11 mph (gentle breeze) occurs around December 31, at which time the average daily maximum wind speed is 17 mph (moderate breeze).

The lowest average wind speed of 10 mph (gentle breeze) occurs around December 11, at which time the average daily maximum wind speed is 17 mph (moderate breeze).

Wind Speed in December

The average daily minimum (red), maximum (green), and average (black) wind speed with percentile bands (inner band from 25th to 75th percentile, outer band from 10th to 90th percentile).
The wind is most often out of the east (36% of the time), north east (19% of the time), and south east (14% of the time). The wind is least often out of the west (0% of the time), north west (0% of the time), south west (1% of the time), and south (2% of the time).

Wind Directions in December

The fraction of time spent with the wind blowing from the various directions over the entire year. Values do not sum to 100% because the wind direction is undefined when the wind speed is zero.

Fraction of Time Spent with Various Wind Directions in December

The fraction of time spent with the wind blowing from the various directions on a daily basis. Stacked values do not always sum to 100% because the wind direction is undefined when the wind speed is zero.