Average Weather in December in Altamont Oregon, United States
In Altamont, the month of December is characterized by gradually falling daily high temperatures, with daily highs decreasing by 3°F, from 41°F to 38°F over the course of the month, and rarely exceeding 51°F or dropping below 28°F. The lowest daily average high temperature is 38°F on December 26.
Daily low temperatures decrease by 3°F, from 25°F to 22°F, rarely falling below 8°F or exceeding 36°F. The lowest daily average low temperature is 22°F on December 23.
For reference, on August 4, the hottest day of the year, temperatures in Altamont typically range from 50°F to 85°F, while on December 23, the coldest day of the year, they range from 22°F to 38°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 Altamont experiences essentially constant cloud cover, with the percentage of time that the sky is overcast or mostly cloudy remaining about 65% throughout the month.
The clearest day of the month is December 13, with clear, mostly clear, or partly cloudy conditions 36% of the time.
For reference, on January 10, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 67%, while on August 3, the clearest day of the year, the chance of clear, mostly clear, or partly cloudy skies is 87%.
Cloud Cover Categories in December
A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. In Altamont, the chance of a wet day over the course of December is decreasing, starting the month at 33% and ending it at 28%.
For reference, the year's highest daily chance of a wet day is 33% on November 30, and its lowest chance is 4% on August 4.
Over the course of December in Altamont, the chance of a day with only rain decreases from 21% to 14%, the chance of a day with mixed snow and rain remains an essentially constant 8% throughout, and the chance of a day with only snow increases from 4% to 6%.
Probability of Precipitation in December
The average sliding 31-day rainfall during December in Altamont is gradually decreasing, starting the month at 2.3 inches, when it rarely exceeds 4.8 inches or falls below 0.5 inches, and ending the month at 2.1 inches, when it rarely exceeds 5.1 inches or falls below 0.2 inches.
The highest average 31-day accumulation is 2.4 inches on December 9.
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 Altamont is essentially constant, remaining about 0.5 inches throughout, and rarely exceeding 1.6 inches or falling to 0.0 inches.
The highest average 31-day liquid-equivalent accumulation is 0.6 inches on December 22.
Average Monthly Liquid-Equivalent Snowfall in December
Over the course of December in Altamont, 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, 19 minutes of daylight.
Hours of Daylight and Twilight in December
The earliest sunrise of the month in Altamont is 7:16 AM on December 1 and the latest sunrise is 19 minutes later at 7:35 AM on December 31.
The earliest sunset is 4:34 PM on December 8 and the latest sunset is 10 minutes later at 4:44 PM on December 31.
Daylight saving time is observed in Altamont 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 5:30 AM and sets 15 hours, 16 minutes later, at 8:46 PM, while on December 21, the shortest day of the year, it rises at 7:32 AM and sets 9 hours, 6 minutes later, at 4:38 PM.
Sunrise & Sunset with Twilight and Daylight Saving Time in December
The chance that a given day will be muggy in Altamont is essentially constant during December, remaining around 0% throughout.
For reference, on July 9, 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 Altamont is essentially constant during December, remaining within 0.1 miles per hour of 6.7 miles per hour throughout.
For reference, on March 16, the windiest day of the year, the daily average wind speed is 6.9 miles per hour, while on August 3, the calmest day of the year, the daily average wind speed is 4.9 miles per hour.
The highest daily average wind speed during December is 6.8 miles per hour on December 1.
Average Wind Speed in December
Wind Direction in December
The average daily incident shortwave solar energy in Altamont is essentially constant during December, remaining within 0.1 kWh of 1.7 kWh throughout.
The lowest average daily incident shortwave solar energy during December is 1.7 kWh on December 16.
Average Daily Incident Shortwave Solar Energy in December
For the purposes of this report, the geographical coordinates of Altamont are 42.207 deg latitude, -121.737 deg longitude, and 4,150 ft elevation.
The topography within 2 miles of Altamont contains significant variations in elevation, with a maximum elevation change of 627 feet and an average elevation above sea level of 4,168 feet. Within 10 miles contains significant variations in elevation (2,415 feet). Within 50 miles contains large variations in elevation (7,825 feet).
The area within 2 miles of Altamont is covered by artificial surfaces (49%), shrubs (37%), and cropland (10%), within 10 miles by shrubs (53%) and cropland (31%), and within 50 miles by shrubs (52%) and trees (33%).
This report illustrates the typical weather in Altamont 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 Altamont.
For each station, the records are corrected for the elevation difference between that station and Altamont 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 Altamont is computed as the weighted average of the individual contributions from each station, with weights proportional to the inverse of the distance between Altamont and a given station.
Time zones for aiports and weather stations are provided by AskGeo.com .