Average Weather in December in Ontario Oregon, United States
In Ontario, the month of December is characterized by falling daily high temperatures, with daily highs decreasing by 7°F, from 41°F to 34°F over the course of the month, and rarely exceeding 52°F or dropping below 22°F.
Daily low temperatures decrease by 5°F, from 27°F to 22°F, rarely falling below 7°F or exceeding 38°F.
For reference, on July 26, the hottest day of the year, temperatures in Ontario typically range from 62°F to 93°F, while on January 1, the coldest day of the year, they range from 22°F to 34°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 Ontario experiences essentially constant cloud cover, with the percentage of time that the sky is overcast or mostly cloudy remaining about 58% throughout the month.
The clearest day of the month is December 10, with clear, mostly clear, or partly cloudy conditions 43% of the time.
For reference, on January 11, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 60%, while on July 28, the clearest day of the year, the chance of clear, mostly clear, or partly cloudy skies is 84%.
Cloud Cover Categories in December
A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. In Ontario, the chance of a wet day over the course of December is gradually decreasing, starting the month at 24% and ending it at 22%.
For reference, the year's highest daily chance of a wet day is 24% on December 1, and its lowest chance is 3% on July 29.
Over the course of December in Ontario, the chance of a day with only rain decreases from 17% to 10%, the chance of a day with mixed snow and rain remains an essentially constant 4% throughout, and the chance of a day with only snow increases from 3% to 7%.
Probability of Precipitation in December
The average sliding 31-day rainfall during December in Ontario is essentially constant, remaining about 0.9 inches throughout, and rarely exceeding 2.2 inches or falling below 0.1 inches.
The highest average 31-day accumulation is 1.0 inches on December 6.
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 Ontario is essentially constant, remaining about 0.4 inches throughout, and rarely exceeding 1.1 inches or falling to 0.0 inches.
The highest average 31-day liquid-equivalent accumulation is 0.5 inches on December 27.
Average Monthly Liquid-Equivalent Snowfall in December
Over the course of December in Ontario, the length of the day is essentially constant. The shortest day of the month is December 21, with 8 hours, 53 minutes of daylight and the longest day is December 1, with 9 hours, 8 minutes of daylight.
Hours of Daylight and Twilight in December
The earliest sunrise of the month in Ontario is 8:03 AM on December 1 and the latest sunrise is 20 minutes later at 8:22 AM on December 31.
The earliest sunset is 5:09 PM on December 9 and the latest sunset is 10 minutes later at 5:19 PM on December 31.
Daylight saving time is observed in Ontario 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 6:05 AM and sets 15 hours, 29 minutes later, at 9:34 PM, while on December 21, the shortest day of the year, it rises at 8:19 AM and sets 8 hours, 53 minutes later, at 5:12 PM.
Sunrise & Sunset with Twilight and Daylight Saving Time in December
The chance that a given day will be muggy in Ontario is essentially constant during December, remaining around 0% throughout.
For reference, on August 3, the muggiest day of the year, there are muggy conditions 0% of the time, while on September 23, 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 Ontario is essentially constant during December, remaining within 0.2 miles per hour of 5.9 miles per hour throughout.
For reference, on April 11, the windiest day of the year, the daily average wind speed is 7.3 miles per hour, while on January 10, the calmest day of the year, the daily average wind speed is 5.6 miles per hour.
The highest daily average wind speed during December is 6.1 miles per hour on December 1.
Average Wind Speed in December
Wind Direction in December
The average daily incident shortwave solar energy in Ontario is essentially constant during December, remaining within 0.1 kWh of 1.6 kWh throughout.
The lowest average daily incident shortwave solar energy during December is 1.5 kWh on December 22.
Average Daily Incident Shortwave Solar Energy in December
For the purposes of this report, the geographical coordinates of Ontario are 44.027 deg latitude, -116.963 deg longitude, and 2,156 ft elevation.
The topography within 2 miles of Ontario is essentially flat, with a maximum elevation change of 82 feet and an average elevation above sea level of 2,159 feet. Within 10 miles is essentially flat (945 feet). Within 50 miles contains very significant variations in elevation (6,135 feet).
The area within 2 miles of Ontario is covered by artificial surfaces (50%), cropland (26%), and shrubs (23%), within 10 miles by cropland (65%) and grassland (19%), and within 50 miles by shrubs (55%) and grassland (20%).
This report illustrates the typical weather in Ontario 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 Ontario.
For each station, the records are corrected for the elevation difference between that station and Ontario 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 Ontario is computed as the weighted average of the individual contributions from each station, with weights proportional to the inverse of the distance between Ontario and a given station.
The stations contributing to this reconstruction are: Ontario Municipal Airport (97%, 4.1 kilometers, west); Caldwell Industrial Airport (2.3%, 50 kilometers, southeast); and McCall Airport (0.5%, 118 kilometers, northeast).
Time zones for aiports and weather stations are provided by AskGeo.com .