Average Weather in December in Decatur Michigan, United States
In Decatur, the month of December is characterized by falling daily high temperatures, with daily highs decreasing by 8°F, from 41°F to 33°F over the course of the month, and rarely exceeding 55°F or dropping below 20°F.
Daily low temperatures decrease by 8°F, from 30°F to 22°F, rarely falling below 8°F or exceeding 41°F.
For reference, on July 19, the hottest day of the year, temperatures in Decatur typically range from 63°F to 82°F, while on January 29, the coldest day of the year, they range from 19°F to 31°F.
Average High and Low Temperature in December
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
The month of December in Decatur experiences gradually increasing cloud cover, with the percentage of time that the sky is overcast or mostly cloudy increasing from 61% to 68%. The highest chance of overcast or mostly cloudy conditions is 68% on December 31.
The clearest day of the month is December 1, with clear, mostly clear, or partly cloudy conditions 39% of the time.
For reference, on December 29, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 68%, while on August 26, the clearest day of the year, the chance of clear, mostly clear, or partly cloudy skies is 69%.
Cloud Cover in December
A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. In Decatur, the chance of a wet day over the course of December is gradually decreasing, starting the month at 26% and ending it at 23%.
For reference, the year's highest daily chance of a wet day is 35% on July 30, and its lowest chance is 17% on February 3.
Over the course of December in Decatur, the chance of a day with only rain decreases from 18% to 11%, 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 4% to 9%.
Probability of Precipitation in December
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 Decatur is decreasing, starting the month at 1.9 inches, when it rarely exceeds 3.3 inches or falls below 0.8 inches, and ending the month at 1.2 inches, when it rarely exceeds 2.7 inches or falls below 0.1 inches.
Average Monthly Rainfall in December
We report snowfall in liquid-equivalent terms. The actual depth of new snowfall is typically between 5 and 10 times the liquid-equivalent amount, assuming the ground is frozen. As with rainfall, we consider the liquid-equivalent snowfall accumulated over a sliding 31-day period centered around each day.
The average sliding 31-day liquid-equivalent snowfall during December in Decatur is essentially constant, remaining about 0.4 inches throughout, and rarely exceeding 1.2 inches or falling to 0.0 inches.
Average Monthly Liquid-Equivalent Snowfall in December
Over the course of December in Decatur, the length of the day is essentially constant. The shortest day of the month is December 21, with 9 hours, 6 minutes of daylight and the longest day is December 1, with 9 hours, 20 minutes of daylight.
Hours of Daylight and Twilight in December
The earliest sunrise of the month in Decatur is 7:52 AM on December 1 and the latest sunrise is 19 minutes later at 8:12 AM on December 31.
The earliest sunset is 5:12 PM on December 8 and the latest sunset is 10 minutes later at 5:22 PM on December 31.
Daylight saving time is observed in Decatur during 2017, 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 6:08 AM and sets 15 hours, 15 minutes later, at 9:23 PM, while on December 21, the shortest day of the year, it rises at 8:09 AM and sets 9 hours, 6 minutes later, at 5:15 PM.
Sunrise & Sunset with Twilight and Daylight Saving Time in December
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 Decatur is essentially constant during December, remaining around 0% throughout.
For reference, on July 28, the muggiest day of the year, there are muggy conditions 40% of the time, while on January 1, the least muggy day of the year, there are muggy conditions 0% of the time.
Humidity Comfort Levels in December
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 Decatur is essentially constant during December, remaining within 0.2 miles per hour of 7.1 miles per hour throughout.
For reference, on January 15, the windiest day of the year, the daily average wind speed is 7.4 miles per hour, while on August 4, the calmest day of the year, the daily average wind speed is 4.3 miles per hour.
Average Wind Speed in December
Wind Direction in December
Decatur 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 in Decatur is decreasing during December, falling by 5°F, from 45°F to 40°F, over the course of the month.
Average Water Temperature in December
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 Decatur is essentially constant during December, remaining within 0.1 kWh of 1.5 kWh throughout.
The lowest average daily incident shortwave solar energy during December is 1.4 kWh on December 23.
Average Daily Incident Shortwave Solar Energy in December
For the purposes of this report, the geographical coordinates of Decatur are 42.108 deg latitude, -85.974 deg longitude, and 758 ft elevation.
The topography within 2 miles of Decatur is essentially flat, with a maximum elevation change of 75 feet and an average elevation above sea level of 759 feet. Within 10 miles is essentially flat (387 feet). Within 50 miles contains only modest variations in elevation (574 feet).
The area within 2 miles of Decatur is covered by cropland (63%), trees (21%), and artificial surfaces (12%), within 10 miles by cropland (63%) and trees (32%), and within 50 miles by cropland (51%) and water (21%).
This report illustrates the typical weather in Decatur year round, 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 5 weather stations near enough to contribute to our estimation of the temperature and dew point in Decatur.
For each station, the records are corrected for the elevation difference between that station and Decatur 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 Decatur is computed as the weighted average of the individual contributions from each station, with weights proportional to the inverse of the distance between Decatur and a given station.
The stations contributing to this reconstruction are: Hree Rivers Municipal Dr Haines Airport (23%, 36 kilometers, southeast); South Haven Area Regional Airport (23%, 36 kilometers, northwest); Ross Field-Twin Cities Airport (21%, 38 kilometers, west); Kalamazoo-Battle Creek International Airport (21%, 38 kilometers, east); and Michigan City Municipal Airport-Phillips Field (13%, 52 kilometers, southwest).
All data relating to the Sun's position (e.g., sunrise and sunset) are computed using astronomical formulas from the book, Astronomical Tables of the Sun, Moon and Planets , 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 aiports and weather stations are provided by AskGeo.com .
Maps are © Esri, with data from National Geographic, Esri, DeLorme, NAVTEQ, UNEP-WCMC, USGS, NASA, ESA, METI, NRCAN, GEBCO, NOAA, and iPC.