Average Weather in December in Mountlake Terrace Washington, United States
Daily high temperatures decrease by 2°F, from 47°F to 45°F, rarely falling below 37°F or exceeding 54°F. The lowest daily average high temperature is 45°F on December 23.
Daily low temperatures are around 38°F, rarely falling below 28°F or exceeding 46°F. The lowest daily average low temperature is 37°F on December 23.
For reference, on August 3, the hottest day of the year, temperatures in Mountlake Terrace typically range from 57°F to 76°F, while on December 23, the coldest day of the year, they range from 37°F to 45°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 Mountlake Terrace experiences essentially constant cloud cover, with the percentage of time that the sky is overcast or mostly cloudy remaining about 71% throughout the month.
The clearest day of the month is December 31, with clear, mostly clear, or partly cloudy conditions 29% of the time.
For reference, on January 19, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 72%, while on August 3, the clearest day of the year, the chance of clear, mostly clear, or partly cloudy skies is 75%.
Cloud Cover Categories in December
A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. In Mountlake Terrace, the chance of a wet day over the course of December is rapidly decreasing, starting the month at 56% and ending it at 49%.
For reference, the year's highest daily chance of a wet day is 58% on November 18, and its lowest chance is 9% on August 11.
Over the course of December in Mountlake Terrace, the chance of a day with only rain decreases from 54% to 46%, the chance of a day with mixed snow and rain remains an essentially constant 2% throughout, and the chance of a day with only snow remains an essentially constant 1% throughout.
Probability of Precipitation in December
The average sliding 31-day rainfall during December in Mountlake Terrace is rapidly decreasing, starting the month at 7.6 inches, when it rarely exceeds 11.7 inches or falls below 3.4 inches, and ending the month at 6.3 inches, when it rarely exceeds 9.7 inches or falls below 3.2 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 Mountlake Terrace is essentially constant, remaining about 0.1 inches throughout, and rarely exceeding 0.7 inches or falling to 0.0 inches.
The highest average 31-day liquid-equivalent accumulation is 0.2 inches on December 30.
Average Monthly Liquid-Equivalent Snowfall in December
Over the course of December in Mountlake Terrace, the length of the day is essentially constant. The shortest day of the month is December 21, with 8 hours, 24 minutes of daylight and the longest day is December 1, with 8 hours, 42 minutes of daylight.
Hours of Daylight and Twilight in December
The earliest sunrise of the month in Mountlake Terrace is 7:37 AM on December 1 and the latest sunrise is 21 minutes later at 7:58 AM on December 31.
The earliest sunset is 4:16 PM on December 11 and the latest sunset is 10 minutes later at 4:26 PM on December 31.
Daylight saving time is observed in Mountlake 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 5:10 AM and sets 16 hours, 1 minute later, at 9:11 PM, while on December 21, the shortest day of the year, it rises at 7:55 AM and sets 8 hours, 24 minutes later, at 4:19 PM.
Sunrise & Sunset with Twilight and Daylight Saving Time in December
The chance that a given day will be muggy in Mountlake Terrace is essentially constant during December, remaining around 0% throughout.
For reference, on July 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 Mountlake Terrace is essentially constant during December, remaining within 0.1 miles per hour of 5.0 miles per hour throughout.
For reference, on December 4, the windiest day of the year, the daily average wind speed is 5.2 miles per hour, while on August 2, the calmest day of the year, the daily average wind speed is 2.5 miles per hour.
The highest daily average wind speed during December is 5.2 miles per hour on December 4.
Average Wind Speed in December
Wind Direction in December
Mountlake 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 Mountlake Terrace is gradually decreasing during December, falling by 2°F, from 49°F to 47°F, over the course of the month.
Average Water Temperature in December
The growing season in Mountlake Terrace typically lasts for 9.2 months (279 days), from around February 20 to around November 26, rarely starting before January 19 or after March 14, and rarely ending before November 3 or after December 19.
The month of December in Mountlake Terrace is more likely than not fully outside of the growing season, with the chance that a given day is in the growing season rapidly decreasing from 40% to 5% over the course of the month.
Time Spent in Various Temperature Bands and the Growing Season in December
The average accumulated growing degree days in Mountlake Terrace are essentially constant during December, remaining within 3°F of 1,932°F throughout.
Growing Degree Days in December
The average daily incident shortwave solar energy in Mountlake Terrace is essentially constant during December, remaining within 0.1 kWh of 1.0 kWh throughout.
The lowest average daily incident shortwave solar energy during December is 0.9 kWh on December 25.
Average Daily Incident Shortwave Solar Energy in December
For the purposes of this report, the geographical coordinates of Mountlake Terrace are 47.788 deg latitude, -122.309 deg longitude, and 381 ft elevation.
The topography within 2 miles of Mountlake Terrace contains only modest variations in elevation, with a maximum elevation change of 420 feet and an average elevation above sea level of 374 feet. Within 10 miles contains only modest variations in elevation (640 feet). Within 50 miles contains significant variations in elevation (7,720 feet).
The area within 2 miles of Mountlake Terrace is covered by artificial surfaces (98%), within 10 miles by artificial surfaces (53%) and water (32%), and within 50 miles by trees (50%) and water (18%).
This report illustrates the typical weather in Mountlake 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 2 weather stations near enough to contribute to our estimation of the temperature and dew point in Mountlake Terrace.
For each station, the records are corrected for the elevation difference between that station and Mountlake 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 Mountlake Terrace is computed as the weighted average of the individual contributions from each station, with weights proportional to the inverse of the distance between Mountlake Terrace and a given station.
Time zones for aiports and weather stations are provided by AskGeo.com .