Average Weather in December in Coulee Dam Washington, United States
Daily high temperatures decrease by 6°F, from 36°F to 30°F, rarely falling below 18°F or exceeding 45°F. The lowest daily average high temperature is 30°F on December 30.
Daily low temperatures decrease by 5°F, from 25°F to 21°F, rarely falling below 7°F or exceeding 35°F.
For reference, on July 31, the hottest day of the year, temperatures in Coulee Dam typically range from 61°F to 90°F, while on January 1, the coldest day of the year, they range from 21°F to 30°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
Ivanivka, Ukraine (5,630 miles away); Kemaliye, Turkey (6,260 miles); and Suluktu, Kyrgyzstan (6,348 miles) are the far-away foreign places with temperatures most similar to Coulee Dam (view comparison).
The month of December in Coulee Dam experiences essentially constant cloud cover, with the percentage of time that the sky is overcast or mostly cloudy remaining about 68% throughout the month.
The clearest day of the month is December 8, with clear, mostly clear, or partly cloudy conditions 33% of the time.
For reference, on January 15, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 70%, while on August 3, the clearest day of the year, the chance of clear, mostly clear, or partly cloudy skies is 79%.
Cloud Cover Categories in December
A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. In Coulee Dam, the chance of a wet day over the course of December is rapidly decreasing, starting the month at 28% and ending it at 21%.
For reference, the year's highest daily chance of a wet day is 28% on November 28, and its lowest chance is 5% on August 18.
Over the course of December in Coulee Dam, the chance of a day with only rain decreases from 14% to 5%, the chance of a day with mixed snow and rain decreases from 7% to 4%, and the chance of a day with only snow increases from 7% to 12%.
Probability of Precipitation in December
The average sliding 31-day rainfall during December in Coulee Dam is gradually decreasing, starting the month at 1.0 inches, when it rarely exceeds 2.3 inches or falls below 0.1 inches, and ending the month at 0.5 inches, when it rarely exceeds 1.2 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 Coulee Dam is essentially constant, remaining about 0.6 inches throughout, and rarely exceeding 1.4 inches or falling below 0.1 inches.
The highest average 31-day liquid-equivalent accumulation is 0.7 inches on December 28.
Average Monthly Liquid-Equivalent Snowfall in December
Over the course of December in Coulee Dam, the length of the day is essentially constant. The shortest day of the month is December 21, with 8 hours, 23 minutes of daylight and the longest day is December 1, with 8 hours, 40 minutes of daylight.
Hours of Daylight and Twilight in December
The earliest sunrise of the month in Coulee Dam is 7:24 AM on December 1 and the latest sunrise is 21 minutes later at 7:45 AM on December 31.
The earliest sunset is 4:02 PM on December 11 and the latest sunset is 10 minutes later at 4:12 PM on December 31.
Daylight saving time is observed in Coulee Dam 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 4:56 AM and sets 16 hours, 3 minutes later, at 8:59 PM, while on December 21, the shortest day of the year, it rises at 7:42 AM and sets 8 hours, 23 minutes later, at 4:05 PM.
Sunrise & Sunset with Twilight and Daylight Saving Time in December
The chance that a given day will be muggy in Coulee Dam is essentially constant during December, remaining around 0% throughout.
For reference, on July 17, the muggiest day of the year, there are muggy conditions 0% 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
The average hourly wind speed in Coulee Dam is essentially constant during December, remaining within 0.2 miles per hour of 6.1 miles per hour throughout.
For reference, on March 26, the windiest day of the year, the daily average wind speed is 7.0 miles per hour, while on January 5, the calmest day of the year, the daily average wind speed is 5.9 miles per hour.
Average Wind Speed in December
Wind Direction in December
The growing season in Coulee Dam typically lasts for 5.7 months (173 days), from around April 24 to around October 14, rarely starting before April 5 or after May 13, and rarely ending before September 27 or after October 31.
The month of December in Coulee Dam is reliably fully outside of the growing season.
Time Spent in Various Temperature Bands and the Growing Season in December
The average accumulated growing degree days in Coulee Dam are essentially constant during December, remaining around 2,788°F throughout.
Growing Degree Days in December
The average daily incident shortwave solar energy in Coulee Dam is essentially constant during December, remaining within 0.1 kWh of 1.1 kWh throughout.
The lowest average daily incident shortwave solar energy during December is 1.0 kWh on December 26.
Average Daily Incident Shortwave Solar Energy in December
For the purposes of this report, the geographical coordinates of Coulee Dam are 47.965 deg latitude, -118.976 deg longitude, and 1,768 ft elevation.
The topography within 2 miles of Coulee Dam contains very significant variations in elevation, with a maximum elevation change of 1,539 feet and an average elevation above sea level of 1,633 feet. Within 10 miles contains very significant variations in elevation (3,510 feet). Within 50 miles also contains extreme variations in elevation (6,355 feet).
The area within 2 miles of Coulee Dam is covered by shrubs (84%) and water (14%), within 10 miles by shrubs (68%) and cropland (11%), and within 50 miles by shrubs (48%) and cropland (16%).
This report illustrates the typical weather in Coulee Dam 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 Coulee Dam.
For each station, the records are corrected for the elevation difference between that station and Coulee Dam 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 Coulee Dam is computed as the weighted average of the individual contributions from each station, with weights proportional to the inverse of the distance between Coulee Dam and a given station.
The stations contributing to this reconstruction are: Omak Airport (44%, 68 kilometers, northwest); Ephrata Municipal Airport (33%, 84 kilometers, southwest); and Fairchild Air Force Base (23%, 106 kilometers, east).
Time zones for aiports and weather stations are provided by AskGeo.com .