Average Weather in December in Imperial California, United States
Daily high temperatures decrease by 4°F, from 72°F to 68°F, rarely falling below 60°F or exceeding 79°F. The lowest daily average high temperature is 68°F on December 25.
Daily low temperatures decrease by 3°F, from 46°F to 42°F, rarely falling below 34°F or exceeding 54°F.
For reference, on July 22, the hottest day of the year, temperatures in Imperial typically range from 80°F to 107°F, while on January 1, the coldest day of the year, they range from 42°F to 68°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 Imperial experiences essentially constant cloud cover, with the percentage of time that the sky is overcast or mostly cloudy remaining about 30% throughout the month. The highest chance of overcast or mostly cloudy conditions is 32% on December 28.
The clearest day of the month is December 9, with clear, mostly clear, or partly cloudy conditions 71% of the time.
For reference, on February 20, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 35%, while on September 18, the clearest day of the year, the chance of clear, mostly clear, or partly cloudy skies is 90%.
Cloud Cover Categories in December
A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. In Imperial, the chance of a wet day over the course of December is gradually increasing, starting the month at 7% and ending it at 9%.
For reference, the year's highest daily chance of a wet day is 11% on February 17, and its lowest chance is 1% on June 26.
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 Imperial is essentially constant, remaining about 0.6 inches throughout, and rarely exceeding 1.9 inches.
Average Monthly Rainfall in December
Over the course of December in Imperial, the length of the day is essentially constant. The shortest day of the month is December 21, with 9 hours, 59 minutes of daylight and the longest day is December 1, with 10 hours, 9 minutes of daylight.
Hours of Daylight and Twilight in December
The earliest sunrise of the month in Imperial is 6:26 AM on December 1 and the latest sunrise is 18 minutes later at 6:44 AM on December 31.
The earliest sunset is 4:35 PM on December 4 and the latest sunset is 11 minutes later at 4:46 PM on December 31.
Daylight saving time is observed in Imperial during 2018, 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 5:34 AM and sets 14 hours, 19 minutes later, at 7:53 PM, while on December 21, the shortest day of the year, it rises at 6:40 AM and sets 9 hours, 59 minutes later, at 4:40 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 Imperial is essentially constant during December, remaining around 0% throughout.
For reference, on August 12, the muggiest day of the year, there are muggy conditions 37% of the time, while on November 21, 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 Imperial is essentially constant during December, remaining within 0.1 miles per hour of 6.6 miles per hour throughout.
For reference, on May 7, the windiest day of the year, the daily average wind speed is 9.6 miles per hour, while on January 11, the calmest day of the year, the daily average wind speed is 6.5 miles per hour.
Average Wind Speed in December
Wind Direction in December
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).
While it does not do so every year, freezing temperatures are seen in Imperial over some winters. The day least likely to be in the growing season is January 1, with a 63% chance.
Time Spent in Various Temperature Bands and the Growing Season in December
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 Imperial are increasing during December, increasing by 209°F, from 7,589°F to 7,798°F, over the course of the month.
Growing Degree Days 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 Imperial is essentially constant during December, remaining within 0.1 kWh of 3.4 kWh throughout.
The lowest average daily incident shortwave solar energy during December is 3.3 kWh on December 22.
Average Daily Incident Shortwave Solar Energy in December
For the purposes of this report, the geographical coordinates of Imperial are 32.848 deg latitude, -115.569 deg longitude, and -56 ft elevation.
The topography within 2 miles of Imperial is essentially flat, with a maximum elevation change of 23 feet and an average elevation above sea level of -56 feet. Within 10 miles is essentially flat (308 feet). Within 50 miles contains only modest variations in elevation (6,565 feet).
The area within 2 miles of Imperial is covered by cropland (71%) and shrubs (29%), within 10 miles by cropland (85%), and within 50 miles by shrubs (50%) and bare soil (20%).
This report illustrates the typical weather in Imperial 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 2 weather stations near enough to contribute to our estimation of the temperature and dew point in Imperial.
For each station, the records are corrected for the elevation difference between that station and Imperial 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 Imperial is computed as the weighted average of the individual contributions from each station, with weights proportional to the inverse of the distance between Imperial and a given station.
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.
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.