This report describes the typical weather at the General Rafael Buelna International Airport (Mazatlán, Mexico) weather station over the course of an average December. It is based on the historical records from 1990 to 2012. Earlier records are either unavailable or unreliable.

Mazatlán has a tropical savanna climate with dry winters. The area within 25 mi of this station is covered by forests (54%), oceans and seas (40%), and lakes and rivers (3%).

The month of December is characterized by gradually falling daily high temperatures, with daily highs around 82°F throughout the month, exceeding 87°F or dropping below 76°F only one day in ten.

Daily High and Low Temperature in December

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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).

Fraction of Time Spent in Various Temperature Bands in December

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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).

Over the course of December, the length of the day is essentially constant. The shortest day of the month is December 23 with 10:43 hours of daylight; the longest day is December 1 with 10:48 hours of daylight.

Daily Hours of Daylight and Twilight in December

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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 6:30am on December 1; the latest sunset is at 5:31pm on December 31; the latest sunrise is at 6:46am on December 31; the earliest sunset is at 5:19pm on December 1.

Daylight savings time is observed in 2012 but it neither starts nor ends in December, so the entire month is in standard time.

Daily Sunrise & Sunset with Twilight and Daylight Savings Time 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. The transitions to and from daylight savings time are indicated by the "DST" labels.

The median cloud cover ranges from 20% (mostly clear) to 28% (mostly clear). The trend is for the sky to be becoming cloudier with the median cloud cover increasing by 8% from the start to the end of the month.

Median Cloud Cover in December

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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 40% of the time, partly cloudy 11% of the time, and mostly cloudy or overcast 20% 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.

The average probability that some form of precipitation will be observed in a given day is 7%, with little variation over the course of the month.

Probability of Precipitation at Some Point in the Day in December

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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 thunderstorms.

Light rain is the most severe precipitation observed during 49% of those days with precipitation. It is most likely around December 4, when it is observed during 4% 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 2% of all days.

Thunderstorms are the most severe precipitation observed during 14% of those days with precipitation. They are most likely around December 1, when it is observed during 2% of all days.

Types of Precipitation Throughout December

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

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 44% (comfortable) to 89% (very humid) over the course of a typical December, rarely dropping below 33% (comfortable) and reaching as high as 95% (very humid).

The air is driest around December 30, at which time the relative humidity drops below 50% (comfortable) three days out of four; it is most humid around December 1, rising above 84% (humid) three days out of four.

Relative Humidity in December

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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 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 49°F (dry) to 65°F (mildy humid) and is rarely below 41°F (dry) or above 70°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.

Dew Point in December

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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).

Over the course of December typical wind speeds vary from 0 mph to 11 mph (calm to gentle breeze), rarely exceeding 18 mph (fresh breeze).

The highest average wind speed of 5 mph (light breeze) occurs around December 19, at which time the average daily maximum wind speed is 11 mph (gentle breeze).

The lowest average wind speed of 5 mph (light breeze) occurs around December 1, at which time the average daily maximum wind speed is 11 mph (gentle breeze).

Wind Speed in December

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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).

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.