December Weather in Harrisburg Pennsylvania, United States
Daily high temperatures decrease by 7°F, from 47°F to 39°F, rarely falling below 27°F or exceeding 60°F.
Daily low temperatures decrease by 7°F, from 33°F to 27°F, rarely falling below 15°F or exceeding 45°F.
For reference, on July 20, the hottest day of the year, temperatures in Harrisburg typically range from 67°F to 86°F, while on January 29, the coldest day of the year, they range from 23°F to 38°F.
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.
Krasnodar, Russia (5,337 miles away) and Shali, Russia (5,666 miles) are the far-away foreign places with temperatures most similar to Harrisburg (view comparison).
The month of December in Harrisburg experiences essentially constant cloud cover, with the percentage of time that the sky is overcast or mostly cloudy remaining about 53% throughout the month.
The clearest day of the month is December 3, with clear, mostly clear, or partly cloudy conditions 49% of the time.
For reference, on January 12, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 57%, while on September 23, the clearest day of the year, the chance of clear, mostly clear, or partly cloudy skies is 66%.
A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. In Harrisburg, the chance of a wet day over the course of December is gradually decreasing, starting the month at 26% and ending it at 22%.
For reference, the year's highest daily chance of a wet day is 38% on June 10, and its lowest chance is 21% on January 28.
Over the course of December in Harrisburg, the chance of a day with only rain decreases from 21% to 13%, the chance of a day with mixed snow and rain remains an essentially constant 4% throughout, and the chance of a day with only snow increases from 2% to 4%.
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 in Harrisburg is rapidly decreasing, starting the month at 3.0 inches, when it rarely exceeds 5.1 inches or falls below 1.0 inches, and ending the month at 1.9 inches, when it rarely exceeds 3.6 inches or falls below 0.4 inches.
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 in Harrisburg is rapidly increasing, starting the month at 2.9 inches, when it rarely exceeds 8.9 inches or falls below -0.0 inches, and ending the month at 6.0 inches, when it rarely exceeds 16.0 inches or falls below 0.2 inches.
Over the course of December in Harrisburg, the length of the day is essentially constant. The shortest day of the month is December 21, with 9 hours, 18 minutes of daylight and the longest day is December 1, with 9 hours, 31 minutes of daylight.
The earliest sunrise of the month in Harrisburg is 7:10 AM on December 1 and the latest sunrise is 19 minutes later at 7:30 AM on December 31.
The earliest sunset is 4:41 PM on December 7 and the latest sunset is 10 minutes later at 4:51 PM on December 31.
Daylight saving time is observed in Harrisburg during 2023, but it neither starts nor ends during December, so the entire month is in standard time.
For reference, on June 21, the longest day of the year, the Sun rises at 5:37 AM and sets 15 hours, 3 minutes later, at 8:40 PM, while on December 22, the shortest day of the year, it rises at 7:27 AM and sets 9 hours, 18 minutes later, at 4:45 PM.
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.
The figure below presents a compact representation of key lunar data for December 2023. 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.
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 in Harrisburg is essentially constant during December, remaining around 0% throughout.
For reference, on August 2, the muggiest day of the year, there are muggy conditions 51% of the time, while on November 27, the least muggy day of the year, there are muggy conditions 0% of the time.
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 in Harrisburg is gradually increasing during December, increasing from 6.2 miles per hour to 6.8 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 7.6 miles per hour, while on August 13, the calmest day of the year, the daily average wind speed is 4.2 miles per hour.
The hourly average wind direction in Harrisburg throughout December is predominantly from the west, with a peak proportion of 44% on December 30.
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 in Harrisburg typically lasts for 6.6 months (202 days), from around April 9 to around October 28, rarely starting before March 23 or after April 25, and rarely ending before October 10 or after November 15.
The month of December in Harrisburg is reliably fully outside of 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 in Harrisburg are essentially constant during December, remaining within 5°F of 3,523°F throughout.
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 in Harrisburg is essentially constant during December, remaining within 0.1 kWh of 1.9 kWh throughout.
The lowest average daily incident shortwave solar energy during December is 1.8 kWh on December 23.
For the purposes of this report, the geographical coordinates of Harrisburg are 40.274 deg latitude, -76.884 deg longitude, and 328 ft elevation.
The topography within 2 miles of Harrisburg contains only modest variations in elevation, with a maximum elevation change of 328 feet and an average elevation above sea level of 353 feet. Within 10 miles contains only modest variations in elevation (1,112 feet). Within 50 miles contains very significant variations in elevation (2,221 feet).
The area within 2 miles of Harrisburg is covered by artificial surfaces (71%) and water (22%), within 10 miles by artificial surfaces (41%) and trees (34%), and within 50 miles by cropland (47%) and trees (44%).
This report illustrates the typical weather in Harrisburg, 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
There are 3 weather stations near enough to contribute to our estimation of the temperature and dew point in Harrisburg.
For each station, the records are corrected for the elevation difference between that station and Harrisburg according to the International Standard Atmosphere , and by the relative change present in the MERRA-2 satellite-era reanalysis between the two locations.
The estimated value at Harrisburg is computed as the weighted average of the individual contributions from each station, with weights proportional to the inverse of the distance between Harrisburg and a given station.
The stations contributing to this reconstruction are:
To get a sense of how much these sources agree with each other, you can view a comparison of Harrisburg and the stations that contribute to our estimates of its temperature history and climate. Please note that each source's contribution is adjusted for elevation and the relative change present in the MERRA-2 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.
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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