Average Weather in December in Mission Oregon, United States
Daily high temperatures decrease by 4°F, from 44°F to 39°F, rarely falling below 24°F or exceeding 56°F. The lowest daily average high temperature is 39°F on December 29.
Daily low temperatures decrease by 4°F, from 33°F to 29°F, rarely falling below 16°F or exceeding 43°F. The lowest daily average low temperature is 29°F on December 29.
For reference, on July 31, the hottest day of the year, temperatures in Mission typically range from 61°F to 90°F, while on December 29, the coldest day of the year, they range from 29°F to 39°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 Mission experiences essentially constant cloud cover, with the percentage of time that the sky is overcast or mostly cloudy remaining about 63% throughout the month.
The clearest day of the month is December 17, with clear, mostly clear, or partly cloudy conditions 38% of the time.
For reference, on January 16, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 65%, while on July 29, the clearest day of the year, the chance of clear, mostly clear, or partly cloudy skies is 83%.
Cloud Cover Categories in December
A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. In Mission, the chance of a wet day over the course of December is decreasing, starting the month at 33% and ending it at 27%.
For reference, the year's highest daily chance of a wet day is 33% on December 1, and its lowest chance is 6% on August 4.
Over the course of December in Mission, the chance of a day with only rain decreases from 28% to 19%, the chance of a day with mixed snow and rain remains an essentially constant 3% throughout, and the chance of a day with only snow remains an essentially constant 3% throughout.
Probability of Precipitation in December
The average sliding 31-day rainfall during December in Mission is essentially constant, remaining about 1.5 inches throughout, and rarely exceeding 2.7 inches or falling below 0.4 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 Mission is essentially constant, remaining about 0.2 inches throughout, and rarely exceeding 0.8 inches or falling below -0.0 inches.
The highest average 31-day liquid-equivalent accumulation is 0.3 inches on December 29.
Average Monthly Liquid-Equivalent Snowfall in December
Over the course of December in Mission, the length of the day is essentially constant. The shortest day of the month is December 21, with 8 hours, 41 minutes of daylight and the longest day is December 1, with 8 hours, 57 minutes of daylight.
Hours of Daylight and Twilight in December
The earliest sunrise of the month in Mission is 7:15 AM on December 1 and the latest sunrise is 20 minutes later at 7:35 AM on December 31.
The earliest sunset is 4:10 PM on December 10 and the latest sunset is 10 minutes later at 4:20 PM on December 31.
Daylight saving time is observed in Mission 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 5:05 AM and sets 15 hours, 43 minutes later, at 8:47 PM, while on December 21, the shortest day of the year, it rises at 7:32 AM and sets 8 hours, 41 minutes later, at 4:13 PM.
Sunrise & Sunset with Twilight and Daylight Saving Time in December
The chance that a given day will be muggy in Mission is essentially constant during December, remaining around 0% throughout.
For reference, on August 24, 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 Mission is essentially constant during December, remaining within 0.2 miles per hour of 9.5 miles per hour throughout.
For reference, on December 1, the windiest day of the year, the daily average wind speed is 9.8 miles per hour, while on September 8, the calmest day of the year, the daily average wind speed is 7.1 miles per hour.
The highest daily average wind speed during December is 9.8 miles per hour on December 1.
Average Wind Speed in December
Wind Direction in December
The growing season in Mission typically lasts for 6.6 months (202 days), from around April 8 to around October 27, rarely starting before March 13 or after April 30, and rarely ending before October 7 or after November 17.
The month of December in Mission 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 Mission are essentially constant during December, remaining within 4°F of 2,916°F throughout.
Growing Degree Days in December
The average daily incident shortwave solar energy in Mission is essentially constant during December, remaining within 0.1 kWh of 1.3 kWh throughout.
The lowest average daily incident shortwave solar energy during December is 1.3 kWh on December 23.
Average Daily Incident Shortwave Solar Energy in December
For the purposes of this report, the geographical coordinates of Mission are 45.670 deg latitude, -118.684 deg longitude, and 1,385 ft elevation.
The topography within 2 miles of Mission contains only modest variations in elevation, with a maximum elevation change of 312 feet and an average elevation above sea level of 1,323 feet. Within 10 miles contains only modest variations in elevation (2,940 feet). Within 50 miles contains large variations in elevation (6,696 feet).
The area within 2 miles of Mission is covered by cropland (47%), grassland (27%), and shrubs (21%), within 10 miles by cropland (48%) and shrubs (26%), and within 50 miles by shrubs (45%) and cropland (26%).
This report illustrates the typical weather in Mission 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 Mission.
For each station, the records are corrected for the elevation difference between that station and Mission 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 Mission is computed as the weighted average of the individual contributions from each station, with weights proportional to the inverse of the distance between Mission and a given station.
The stations contributing to this reconstruction are: Eastern Oregon Regional Airport (83%, 14 kilometers, west); Meacham, Meacham (7%, 27 kilometers, southeast); and Walla Walla Regional Airport (10%, 56 kilometers, northeast).
Time zones for aiports and weather stations are provided by AskGeo.com .