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December Weather at Fort Ritchie Maryland, United States

Daily high temperatures decrease by 7°F, from 46°F to 39°F, rarely falling below 26°F or exceeding 60°F.

Daily low temperatures decrease by 7°F, from 32°F to 26°F, rarely falling below 13°F or exceeding 44°F.

For reference, on July 20, the hottest day of the year, temperatures at Fort Ritchie typically range from 66°F to 84°F, while on January 29, the coldest day of the year, they range from 23°F to 37°F.

Average High and Low Temperature in December at Fort Ritchie

Average High and Low Temperature in December at Fort RitchieDec11223344556677889910101111121213131414151516161717181819192020212122222323242425252626272728282929303031315°F5°F10°F10°F15°F15°F20°F20°F25°F25°F30°F30°F35°F35°F40°F40°F45°F45°F50°F50°F55°F55°F60°F60°F65°F65°F70°F70°FNovJanDec 146°FDec 146°F32°F32°FDec 3139°FDec 3139°F26°F26°FDec 1143°FDec 1143°F30°F30°FDec 2140°FDec 2140°F27°F27°F
The daily average high (red line) and low (blue line) temperature, with 25th to 75th and 10th to 90th percentile bands. The thin dotted lines are the corresponding average perceived temperatures.

The figure below shows you a compact characterization of the hourly average temperatures for the quarter of the year centered on December. The horizontal axis is the day, the vertical axis is the hour of the day, and the color is the average temperature for that hour and day.

Average Hourly Temperature in December at Fort Ritchie

Average Hourly Temperature in December at Fort RitchieDec112233445566778899101011111212131314141515161617171818191920202121222223232424252526262727282829293030313112 AM12 AM2 AM2 AM4 AM4 AM6 AM6 AM8 AM8 AM10 AM10 AM12 PM12 PM2 PM2 PM4 PM4 PM6 PM6 PM8 PM8 PM10 PM10 PM12 AM12 AMNovJanfreezingfreezingvery coldcoldcold
frigid 15°F freezing 32°F very cold 45°F cold 55°F cool 65°F comfortable 75°F warm 85°F hot 95°F sweltering
The average hourly temperature, color coded into bands. The shaded overlays indicate night and civil twilight.

Krasnodar, Russia (5,384 miles away) and Martan-Chu, Russia (5,707 miles) are the far-away foreign places with temperatures most similar to Fort Ritchie (view comparison).

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The month of December at Fort Ritchie experiences essentially constant cloud cover, with the percentage of time that the sky is overcast or mostly cloudy remaining about 52% throughout the month.

The clearest day of the month is December 1, with clear, mostly clear, or partly cloudy conditions 50% of the time.

For reference, on January 12, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 55%, while on September 3, the clearest day of the year, the chance of clear, mostly clear, or partly cloudy skies is 66%.

Cloud Cover Categories in December at Fort Ritchie

Cloud Cover Categories in December at Fort RitchieDec11223344556677889910101111121213131414151516161717181819192020212122222323242425252626272728282929303031310%100%10%90%20%80%30%70%40%60%50%50%60%40%70%30%80%20%90%10%100%0%NovJanDec 150%Dec 150%Dec 3147%Dec 3147%Dec 1148%Dec 1148%Dec 2147%Dec 2147%clearmostly clearpartly cloudymostly cloudyovercast
0% clear 20% mostly clear 40% partly cloudy 60% mostly cloudy 80% overcast 100%
The percentage of time spent in each cloud cover band, categorized by the percentage of the sky covered by clouds.

A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. At Fort Ritchie, the chance of a wet day over the course of December is gradually decreasing, starting the month at 25% and ending it at 22%.

For reference, the year's highest daily chance of a wet day is 39% on June 16, and its lowest chance is 20% on October 19.

Over the course of December at Fort Ritchie, the chance of a day with only rain decreases from 18% to 12%, the chance of a day with mixed snow and rain remains an essentially constant 5% throughout, and the chance of a day with only snow increases from 3% to 5%.

Probability of Precipitation in December at Fort Ritchie

The percentage of days in which various types of precipitation are observed, excluding trace quantities: rain alone, snow alone, and mixed (both rain and snow fell in the same day).

Rainfall

To show variation within the month and not just the monthly total, we show the rainfall accumulated over a sliding 31-day period centered around each day.

The average sliding 31-day rainfall during December at Fort Ritchie is rapidly decreasing, starting the month at 2.7 inches, when it rarely exceeds 4.6 inches or falls below 0.8 inches, and ending the month at 1.5 inches, when it rarely exceeds 3.0 inches or falls below 0.3 inches.

Average Monthly Rainfall in December at Fort Ritchie

The average rainfall (solid line) accumulated over the course of a sliding 31-day period centered on the day in question, with 25th to 75th and 10th to 90th percentile bands. The thin dotted line is the corresponding average snowfall.

Snowfall

As with rainfall, we consider the snowfall accumulated over a sliding 31-day period centered around each day.

The average sliding 31-day snowfall during December at Fort Ritchie is rapidly increasing, starting the month at 4.5 inches, when it rarely exceeds 13.3 inches or falls below -0.0 inches, and ending the month at 8.3 inches, when it rarely exceeds 20.2 inches or falls below 0.8 inches.

Average Monthly Snowfall in December at Fort Ritchie

The average snowfall (solid line) accumulated over the course of a sliding 31-day period centered on the day in question, with 25th to 75th and 10th to 90th percentile bands. The thin dotted line is the corresponding average rainfall.

Over the course of December at Fort Ritchie, the length of the day is essentially constant. The shortest day of the month is December 20, with 9 hours, 21 minutes of daylight and the longest day is December 1, with 9 hours, 33 minutes of daylight.

Hours of Daylight and Twilight in December at Fort Ritchie

Hours of Daylight and Twilight in December at Fort RitchieDec11223344556677889910101111121213131414151516161717181819192020212122222323242425252626272728282929303031310 hr24 hr4 hr20 hr8 hr16 hr12 hr12 hr16 hr8 hr20 hr4 hr24 hr0 hrNovJanDec 219 hr, 21 minDec 219 hr, 21 minnightnightdaydayDec 19 hr, 33 minDec 19 hr, 33 min
The number of hours during which the Sun is visible (black line). From bottom (most yellow) to top (most gray), the color bands indicate: full daylight, twilight (civil, nautical, and astronomical), and full night.

The earliest sunrise of the month at Fort Ritchie is 7:12 AM on December 1 and the latest sunrise is 19 minutes later at 7:30 AM on December 31.

The earliest sunset is 4:45 PM on December 6 and the latest sunset is 10 minutes later at 4:55 PM on December 31.

Daylight saving time is observed at Fort Ritchie during 2024, but it neither starts nor ends during December, so the entire month is in daylight saving time.

For reference, on June 20, the longest day of the year, the Sun rises at 5:41 AM and sets 14 hours, 59 minutes later, at 8:41 PM, while on December 21, the shortest day of the year, it rises at 7:27 AM and sets 9 hours, 21 minutes later, at 4:48 PM.

Sunrise & Sunset with Twilight and Daylight Saving Time in December at Fort Ritchie

Sunrise & Sunset with Twilight and Daylight Saving Time in December at Fort RitchieDec112233445566778899101011111212131314141515161617171818191920202121222223232424252526262727282829293030313112 AM2 AM4 AM6 AM8 AM10 AM12 PM2 PM4 PM6 PM8 PM10 PM12 AMNovJan7:12 AM7:12 AMDec 14:45 PMDec 14:45 PM7:30 AM7:30 AMDec 314:55 PMDec 314:55 PM7:21 AM7:21 AMDec 114:45 PMDec 114:45 PM7:27 AM7:27 AMDec 214:48 PMDec 214:48 PMSolarMidnightSolarMidnightSolarNoonSunriseSunset
The solar day over the course of December. From bottom to top, the black lines are the previous solar midnight, sunrise, solar noon, sunset, and the next solar midnight. The day, twilights (civil, nautical, and astronomical), and night are indicated by the color bands from yellow to gray.

The figure below presents a compact representation of the sun's elevation (the angle of the sun above the horizon) and azimuth (its compass bearing) for every hour of every day in the reporting period. The horizontal axis is the day of the year and the vertical axis is the hour of the day. For a given day and hour of that day, the background color indicates the azimuth of the sun at that moment. The black isolines are contours of constant solar elevation.

Solar Elevation and Azimuth in December at Fort Ritchie

Solar Elevation and Azimuth in December at Fort RitchieDec112233445566778899101011111212131314141515161617171818191920202121222223232424252526262727282829293030313112 AM12 AM2 AM2 AM4 AM4 AM6 AM6 AM8 AM8 AM10 AM10 AM12 PM12 PM2 PM2 PM4 PM4 PM6 PM6 PM8 PM8 PM10 PM10 PM12 AM12 AMNovJan0010102020001010202030
northeastsouthwest
Solar elevation and azimuth over the course of December 2024. The black lines are lines of constant solar elevation (the angle of the sun above the horizon, in degrees). The background color fills indicate the azimuth (the compass bearing) of the sun. The lightly tinted areas at the boundaries of the cardinal compass points indicate the implied intermediate directions (northeast, southeast, southwest, and northwest).

The figure below presents a compact representation of key lunar data for December 2024. The horizontal axis is the day, the vertical axis is the hour of the day, and the colored areas indicate when the moon is above the horizon. The vertical gray bars (new Moons) and blue bars (full Moons) indicate key Moon phases. The label associated with each bar indicates the date and time that the phase is obtained, and the companion time labels indicate the rise and set times of the Moon for the nearest time interval in which the moon is above the horizon.

Moon Rise, Set & Phases in December at Fort Ritchie

Moon Rise, Set & Phases in December at Fort RitchieDec112233445566778899101011111212131314141515161617171818191920202121222223232424252526262727282829293030313112 AM12 AM4 AM4 AM8 AM8 AM12 PM12 PM4 PM4 PM8 PM8 PM12 AM12 AMNovJanNov 18:48 AMNov 18:48 AMNov 154:29 PMNov 154:29 PMDec 11:22 AMDec 11:22 AMDec 154:02 AMDec 154:02 AMDec 305:28 PMDec 305:28 PMJan 135:28 PMJan 135:28 PMJan 297:37 AMJan 297:37 AM7:47 AM7:47 AM5:58 PM5:58 PM4:29 PM4:29 PM7:59 AM7:59 AM7:49 AM7:49 AM4:45 PM4:45 PM3:50 PM3:50 PM8:00 AM8:00 AM7:38 AM7:38 AM4:26 PM4:26 PM4:45 PM4:45 PM8:21 AM8:21 AM7:43 AM7:43 AM5:40 PM5:40 PM
The time in which the moon is above the horizon (light blue area), with new moons (dark gray lines) and full moons (blue lines) indicated. The shaded overlays indicate night and civil twilight.
Dec 2024IlluminationMoonriseMoonsetMoonriseMeridian PassingDistance
1
0%7:49 AMSE4:45 PMSW-12:17 PMS245,356 mi
2
2%8:51 AMSE5:37 PMSW-1:14 PMS243,273 mi
3
7%9:46 AMSE6:37 PMSW-2:12 PMS241,139 mi
4
13%10:33 AMSE7:45 PMWSW-3:09 PMS238,992 mi
5
21%11:11 AMESE8:56 PMWSW-4:04 PMS236,851 mi
6
31%11:44 AMESE10:08 PMWSW-4:55 PMS234,735 mi
7
42%12:11 PMESE11:19 PMWSW-5:44 PMS232,679 mi
8
50%12:36 PME--6:32 PMS230,757 mi
9
66%-12:31 AMW1:00 PME7:19 PMS229,082 mi
10
76%-1:43 AMW1:24 PME8:07 PMS227,808 mi
11
86%-2:57 AMWNW1:51 PMENE8:58 PMS227,109 mi
12
93%-4:13 AMWNW2:23 PMENE9:52 PMS227,146 mi
13
98%-5:32 AMWNW3:02 PMENE10:51 PMS228,031 mi
14
100%-6:49 AMNW3:50 PMNE11:53 PMS229,783 mi
15
100%-8:00 AMNW4:49 PMNE--
16
99%-9:00 AMNW5:55 PMNE12:56 AMS232,312 mi
17
95%-9:48 AMNW7:06 PMENE1:55 AMS235,417 mi
18
90%-10:26 AMWNW8:16 PMENE2:50 AMS238,827 mi
19
82%-10:55 AMWNW9:23 PMENE3:40 AMS242,243 mi
20
74%-11:20 AMWNW10:26 PMENE4:25 AMS245,384 mi
21
64%-11:41 AMW11:27 PME5:07 AMS248,009 mi
22
50%-12:01 PMW-5:46 AMS249,937 mi
23
45%12:26 AME12:20 PMW-6:25 AMS251,055 mi
24
35%1:25 AME12:41 PMWSW-7:04 AMS251,321 mi
25
27%2:25 AMESE1:03 PMWSW-7:44 AMS250,759 mi
26
18%3:27 AMESE1:29 PMWSW-8:28 AMS249,459 mi
27
11%4:31 AMESE2:00 PMWSW-9:15 AMS247,560 mi
28
6%5:36 AMSE2:39 PMSW-10:07 AMS245,241 mi
29
2%6:39 AMSE3:28 PMSW-11:03 AMS242,703 mi
30
0%7:38 AMSE4:26 PMSW-12:02 PMS240,143 mi
31
1%8:28 AMSE5:33 PMSW-1:01 PMS237,739 mi

We base the humidity comfort level on the dew point, as it determines whether perspiration will evaporate from the skin, thereby cooling the body. Lower dew points feel drier and higher dew points feel more humid. Unlike temperature, which typically varies significantly between night and day, dew point tends to change more slowly, so while the temperature may drop at night, a muggy day is typically followed by a muggy night.

The chance that a given day will be muggy at Fort Ritchie is essentially constant during December, remaining around 0% throughout.

The lowest chance of a muggy day during December is 0% on December 20.

For reference, on July 27, the muggiest day of the year, there are muggy conditions 49% of the time, while on December 16, the least muggy day of the year, there are muggy conditions 0% of the time.

Humidity Comfort Levels in December at Fort Ritchie

Humidity Comfort Levels in December at Fort RitchieDec11223344556677889910101111121213131414151516161717181819192020212122222323242425252626272728282929303031310%0%10%10%20%20%30%30%40%40%50%50%60%60%70%70%80%80%90%90%100%100%NovJanDec 200%Dec 200%Dec 10%Dec 10%Dec 310%Dec 310%Dec 110%Dec 110%drydrycomfortablecomfortable
dry 55°F comfortable 60°F humid 65°F muggy 70°F oppressive 75°F miserable
The percentage of time spent at various humidity comfort levels, categorized by dew point.

This section discusses the wide-area hourly average wind vector (speed and direction) at 10 meters above the ground. The wind experienced at any given location is highly dependent on local topography and other factors, and instantaneous wind speed and direction vary more widely than hourly averages.

The average hourly wind speed at Fort Ritchie is gradually increasing during December, increasing from 7.3 miles per hour to 7.8 miles per hour over the course of the month.

For reference, on February 26, the windiest day of the year, the daily average wind speed is 8.7 miles per hour, while on July 31, the calmest day of the year, the daily average wind speed is 5.0 miles per hour.

Average Wind Speed in December at Fort Ritchie

The average of mean hourly wind speeds (dark gray line), with 25th to 75th and 10th to 90th percentile bands.

The hourly average wind direction at Fort Ritchie throughout December is predominantly from the west, with a peak proportion of 44% on December 29.

Wind Direction in December at Fort Ritchie

Wind Direction in December at Fort RitchieDec11223344556677889910101111121213131414151516161717181819192020212122222323242425252626272728282929303031310%100%20%80%40%60%60%40%80%20%100%0%NovJanwestsouthnortheast
northeastsouthwest
The percentage of hours in which the mean wind direction is from each of the four cardinal wind directions, excluding hours in which the mean wind speed is less than 1.0 mph. The lightly tinted areas at the boundaries are the percentage of hours spent in the implied intermediate directions (northeast, southeast, southwest, and northwest).

Fort Ritchie is located near a large body of water (e.g., ocean, sea, or large lake). This section reports on the wide-area average surface temperature of that water.

The average surface water temperature at Fort Ritchie is rapidly decreasing during December, falling by 7°F, from 48°F to 41°F, over the course of the month.

Average Water Temperature in December at Fort Ritchie

Average Water Temperature in December at Fort RitchieDec112233445566778899101011111212131314141515161617171818191920202121222223232424252526262727282829293030313130°F30°F35°F35°F40°F40°F45°F45°F50°F50°F55°F55°F60°F60°F65°F65°FNovJanDec 148°FDec 148°FDec 3141°FDec 3141°FDec 1146°FDec 1146°FDec 2143°FDec 2143°F
The daily average water temperature (purple line), with 25th to 75th and 10th to 90th percentile bands.

Definitions of the growing season vary throughout the world, but for the purposes of this report, we define it as the longest continuous period of non-freezing temperatures (≥ 32°F) in the year (the calendar year in the Northern Hemisphere, or from July 1 until June 30 in the Southern Hemisphere).

The growing season at Fort Ritchie typically lasts for 6.6 months (204 days), from around April 10 to around October 31, rarely starting before March 25 or after April 26, and rarely ending before October 13 or after November 16.

The month of December at Fort Ritchie is reliably fully outside of the growing season.

Time Spent in Various Temperature Bands and the Growing Season in December at Fort Ritchie

Time Spent in Various Temperature Bands and the Growing Season in December at Fort RitchieDec11223344556677889910101111121213131414151516161717181819192020212122222323242425252626272728282929303031310%100%10%90%20%80%30%70%40%60%50%50%60%40%70%30%80%20%90%10%100%0%NovJan-0%Dec 16-0%Dec 16Nov 1610%Nov 1610%frigidfreezingvery coldcoldcoolcomfortable
frigid 15°F freezing 32°F very cold 45°F cold 55°F cool 65°F comfortable 75°F warm 85°F hot 95°F sweltering
The percentage of time spent in various temperature bands. The black line is the percentage chance that a given day is within the growing season.

Growing degree days are a measure of yearly heat accumulation used to predict plant and animal development, and defined as the integral of warmth above a base temperature, discarding any excess above a maximum temperature. In this report, we use a base of 50°F and a cap of 86°F.

The average accumulated growing degree days at Fort Ritchie are essentially constant during December, remaining within 6°F of 3,383°F throughout.

Growing Degree Days in December at Fort Ritchie

Growing Degree Days in December at Fort RitchieDec11223344556677889910101111121213131414151516161717181819192020212122222323242425252626272728282929303031313,100°F3,100°F3,200°F3,200°F3,300°F3,300°F3,400°F3,400°F3,500°F3,500°F3,600°F3,600°F3,700°F3,700°FNovJanDec 13,377°FDec 13,377°FDec 313,389°FDec 313,389°FDec 113,382°FDec 113,382°FDec 213,388°FDec 213,388°F
The average growing degree days accumulated over the course of December, with 25th to 75th and 10th to 90th percentile bands.

This section discusses the total daily incident shortwave solar energy reaching the surface of the ground over a wide area, taking full account of seasonal variations in the length of the day, the elevation of the Sun above the horizon, and absorption by clouds and other atmospheric constituents. Shortwave radiation includes visible light and ultraviolet radiation.

The average daily incident shortwave solar energy at Fort Ritchie is essentially constant during December, remaining within 0.1 kWh of 2.0 kWh throughout.

The lowest average daily incident shortwave solar energy during December is 1.9 kWh on December 24.

Average Daily Incident Shortwave Solar Energy in December at Fort Ritchie

Average Daily Incident Shortwave Solar Energy in December at Fort RitchieDec11223344556677889910101111121213131414151516161717181819192020212122222323242425252626272728282929303031310.0 kWh0.0 kWh0.5 kWh0.5 kWh1.0 kWh1.0 kWh1.5 kWh1.5 kWh2.0 kWh2.0 kWh2.5 kWh2.5 kWh3.0 kWh3.0 kWh3.5 kWh3.5 kWh4.0 kWh4.0 kWhNovJanDec 241.9 kWhDec 241.9 kWhDec 12.1 kWhDec 12.1 kWhDec 111.9 kWhDec 111.9 kWh
The average daily shortwave solar energy reaching the ground per square meter (orange line), with 25th to 75th and 10th to 90th percentile bands.

For the purposes of this report, the geographical coordinates of Fort Ritchie are 39.733 deg latitude, -77.433 deg longitude, and 814 ft elevation.

The topography within 2 miles of Fort Ritchie contains very significant variations in elevation, with a maximum elevation change of 1,004 feet and an average elevation above sea level of 1,085 feet. Within 10 miles also contains very significant variations in elevation (1,818 feet). Within 50 miles contains very significant variations in elevation (2,405 feet).

The area within 2 miles of Fort Ritchie is covered by trees (96%), within 10 miles by trees (57%) and cropland (41%), and within 50 miles by cropland (46%) and trees (45%).

This report illustrates the typical weather at Fort Ritchie, based on a statistical analysis of historical hourly weather reports and model reconstructions from January 1, 1980 to December 31, 2016.

Temperature and Dew Point

Fort Ritchie has a weather station that reported reliably enough during the analysis period that we have included it in our network. When available, historical temperature and dew point measurements are taken directly from this weather station. These records are obtained from NOAA's Integrated Surface Hourly data set, falling back on ICAO METAR records as required.

In the case of missing or erroneous measurements from this station, we fall back on records from nearby stations, adjusted according to typical seasonal and diurnal intra-station differences. For a given day of the year and hour of the day, the fallback station is selected to minimize the prediction error over the years for which there are measurements for both stations.

The stations on which we may fall back include but are not limited to Site R, Frederick Municipal Airport, Hagerstown Regional Airport, Carroll County Regional Airport/Jack B Poage Field, Eastern West Virginia Regional Airport, Montgomery County Airpark, Leesburg Executive Airport, and York Airport.

Other Data

All data relating to the Sun's position (e.g., sunrise and sunset) are computed using astronomical formulas from the book, Astronomical Algorithms 2nd Edition , by Jean Meeus.

All other weather data, including cloud cover, precipitation, wind speed and direction, and solar flux, come from NASA's MERRA-2 Modern-Era Retrospective Analysis . This reanalysis combines a variety of wide-area measurements in a state-of-the-art global meteorological model to reconstruct the hourly history of weather throughout the world on a 50-kilometer grid.

Land Use data comes from the Global Land Cover SHARE database , published by the Food and Agriculture Organization of the United Nations.

Elevation data comes from the Shuttle Radar Topography Mission (SRTM) , published by NASA's Jet Propulsion Laboratory.

Names, locations, and time zones of places and some airports come from the GeoNames Geographical Database .

Time zones for airports and weather stations are provided by AskGeo.com .

Maps are © OpenStreetMap contributors.

Disclaimer

The information on this site is provided as is, without any assurances as to its accuracy or suitability for any purpose. Weather data is prone to errors, outages, and other defects. We assume no responsibility for any decisions made on the basis of the content presented on this site.

We draw particular cautious attention to our reliance on the MERRA-2 model-based reconstructions for a number of important data series. While having the tremendous advantages of temporal and spatial completeness, these reconstructions: (1) are based on computer models that may have model-based errors, (2) are coarsely sampled on a 50 km grid and are therefore unable to reconstruct the local variations of many microclimates, and (3) have particular difficulty with the weather in some coastal areas, especially small islands.

We further caution that our travel scores are only as good as the data that underpin them, that weather conditions at any given location and time are unpredictable and variable, and that the definition of the scores reflects a particular set of preferences that may not agree with those of any particular reader.

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