Average Weather in December in Grand Terrace California, United States
Daily high temperatures decrease by 3°F, from 70°F to 66°F, rarely falling below 55°F or exceeding 80°F. The lowest daily average high temperature is 66°F on December 25.
Daily low temperatures are around 44°F, rarely falling below 36°F or exceeding 52°F. The lowest daily average low temperature is 43°F on December 25.
For reference, on August 19, the hottest day of the year, temperatures in Grand Terrace typically range from 65°F to 96°F, while on December 25, the coldest day of the year, they range from 43°F to 66°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 Grand Terrace experiences gradually increasing cloud cover, with the percentage of time that the sky is overcast or mostly cloudy increasing from 36% to 40%. The highest chance of overcast or mostly cloudy conditions is 41% on December 28.
The clearest day of the month is December 1, with clear, mostly clear, or partly cloudy conditions 64% of the time.
For reference, on February 20, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 46%, while on September 7, the clearest day of the year, the chance of clear, mostly clear, or partly cloudy skies is 90%.
Cloud Cover Categories in December
0% clear 20% mostly clear 40% partly cloudy 60% mostly cloudy 80% overcast 100%
A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. In Grand Terrace, the chance of a wet day over the course of December is increasing, starting the month at 11% and ending it at 15%.
For reference, the year's highest daily chance of a wet day is 19% on February 20, and its lowest chance is 1% on June 20.
Probability of Precipitation in December
The average sliding 31-day rainfall during December in Grand Terrace is increasing, starting the month at 1.1 inches, when it rarely exceeds 2.6 inches or falls below 0.1 inches, and ending the month at 2.0 inches, when it rarely exceeds 5.6 inches or falls below 0.1 inches.
Average Monthly Rainfall in December
Over the course of December in Grand Terrace, the length of the day is essentially constant. The shortest day of the month is December 21, with 9 hours, 53 minutes of daylight and the longest day is December 1, with 10 hours, 3 minutes of daylight.
Hours of Daylight and Twilight in December
The earliest sunrise of the month in Grand Terrace is 6:36 AM on December 1 and the latest sunrise is 18 minutes later at 6:54 AM on December 31.
The earliest sunset is 4:39 PM on December 4 and the latest sunset is 10 minutes later at 4:50 PM on December 31.
Daylight saving time is observed in Grand Terrace 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 5:38 AM and sets 14 hours, 26 minutes later, at 8:03 PM, while on December 21, the shortest day of the year, it rises at 6:50 AM and sets 9 hours, 53 minutes later, at 4:44 PM.
Sunrise & Sunset with Twilight and Daylight Saving Time in December
The chance that a given day will be muggy in Grand Terrace is essentially constant during December, remaining around 0% throughout.
For reference, on July 31, the muggiest day of the year, there are muggy conditions 4% of the time, while on November 3, the least muggy day of the year, there are muggy conditions 0% of the time.
Humidity Comfort Levels in December
dry 55°F comfortable 60°F humid 65°F muggy 70°F oppressive 75°F miserable
The average hourly wind speed in Grand Terrace is essentially constant during December, remaining within 0.2 miles per hour of 7.0 miles per hour throughout.
For reference, on December 31, the windiest day of the year, the daily average wind speed is 7.3 miles per hour, while on September 8, the calmest day of the year, the daily average wind speed is 5.2 miles per hour.
The highest daily average wind speed during December is 7.3 miles per hour on December 31.
Average Wind Speed in December
Wind Direction in December
Grand Terrace 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 Grand Terrace is gradually decreasing during December, falling by 2°F, from 62°F to 59°F, over the course of the month.
Average Water Temperature in December
While it does not do so every year, freezing temperatures are seen in Grand Terrace over some winters. The day least likely to be in the growing season is January 6, with a 68% chance.
Time Spent in Various Temperature Bands and the Growing Season in December
The average accumulated growing degree days in Grand Terrace are gradually increasing during December, increasing by 173°F, from 5,350°F to 5,522°F, over the course of the month.
Growing Degree Days in December
The average daily incident shortwave solar energy in Grand Terrace is essentially constant during December, remaining within 0.2 kWh of 3.2 kWh throughout.
The lowest average daily incident shortwave solar energy during December is 3.0 kWh on December 26.
Average Daily Incident Shortwave Solar Energy in December
For the purposes of this report, the geographical coordinates of Grand Terrace are 34.034 deg latitude, -117.314 deg longitude, and 1,014 ft elevation.
The topography within 2 miles of Grand Terrace contains very significant variations in elevation, with a maximum elevation change of 1,526 feet and an average elevation above sea level of 1,115 feet. Within 10 miles contains very significant variations in elevation (2,408 feet). Within 50 miles contains large variations in elevation (11,490 feet).
The area within 2 miles of Grand Terrace is covered by shrubs (79%) and artificial surfaces (20%), within 10 miles by shrubs (60%) and artificial surfaces (35%), and within 50 miles by shrubs (65%) and artificial surfaces (16%).
This report illustrates the typical weather in Grand Terrace 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 3 weather stations near enough to contribute to our estimation of the temperature and dew point in Grand Terrace.
For each station, the records are corrected for the elevation difference between that station and Grand Terrace 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 Grand Terrace is computed as the weighted average of the individual contributions from each station, with weights proportional to the inverse of the distance between Grand Terrace and a given station.
The stations contributing to this reconstruction are: San Bernardino International Airport (53%, 10 kilometers, northeast); Riverside Municipal Airport (29%, 15 kilometers, southwest); and March Air Reserve Base (18%, 16 kilometers, south).
Time zones for aiports and weather stations are provided by AskGeo.com .