Average Weather in December in Signal Hill California, United States
Daily high temperatures decrease by 2°F, from 68°F to 66°F, rarely falling below 58°F or exceeding 77°F. The lowest daily average high temperature is 66°F on December 25.
Daily low temperatures decrease by 2°F, from 50°F to 48°F, rarely falling below 42°F or exceeding 56°F. The lowest daily average low temperature is 48°F on December 27.
For reference, on August 23, the hottest day of the year, temperatures in Signal Hill typically range from 65°F to 82°F, while on December 27, the coldest day of the year, they range from 48°F to 66°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 Signal Hill experiences gradually increasing cloud cover, with the percentage of time that the sky is overcast or mostly cloudy increasing from 34% to 39%. The highest chance of overcast or mostly cloudy conditions is 39% on December 28.
The clearest day of the month is December 1, with clear, mostly clear, or partly cloudy conditions 66% of the time.
For reference, on February 20, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 42%, while on September 7, the clearest day of the year, the chance of clear, mostly clear, or partly cloudy skies is 91%.
Cloud Cover Categories in December
A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. In Signal Hill, the chance of a wet day over the course of December is increasing, starting the month at 12% and ending it at 18%.
For reference, the year's highest daily chance of a wet day is 21% on February 19, and its lowest chance is 0% on July 2.
Probability of Precipitation in December
To show variation within the month and not just the monthly total, we show the rainfall accumulated over a sliding 31-day period centered around each day.
The average sliding 31-day rainfall during December in Signal Hill is rapidly increasing, starting the month at 1.5 inches, when it rarely exceeds 3.4 inches, and ending the month at 2.5 inches, when it rarely exceeds 6.9 inches or falls below 0.1 inches.
Average Monthly Rainfall in December
Over the course of December in Signal Hill, the length of the day is essentially constant. The shortest day of the month is December 21, with 9 hours, 54 minutes of daylight and the longest day is December 1, with 10 hours, 4 minutes of daylight.
Hours of Daylight and Twilight in December
The earliest sunrise of the month in Signal Hill is 6:39 AM on December 1 and the latest sunrise is 18 minutes later at 6:57 AM on December 31.
The earliest sunset is 4:43 PM on December 4 and the latest sunset is 11 minutes later at 4:54 PM on December 31.
Daylight saving time is observed in Signal Hill 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 5:42 AM and sets 14 hours, 24 minutes later, at 8:06 PM, while on December 21, the shortest day of the year, it rises at 6:53 AM and sets 9 hours, 54 minutes later, at 4:48 PM.
Sunrise & Sunset with Twilight and Daylight Saving Time in December
The chance that a given day will be muggy in Signal Hill is essentially constant during December, remaining around 0% throughout.
For reference, on August 30, the muggiest day of the year, there are muggy conditions 9% 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 Signal Hill is gradually increasing during December, increasing from 7.8 miles per hour to 8.3 miles per hour over the course of the month.
For reference, on December 30, the windiest day of the year, the daily average wind speed is 8.3 miles per hour, while on August 14, the calmest day of the year, the daily average wind speed is 5.1 miles per hour.
The highest daily average wind speed during December is 8.3 miles per hour on December 31.
Average Wind Speed in December
Wind Direction in December
Signal Hill 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 Signal Hill is gradually decreasing during December, falling by 2°F, from 62°F to 59°F, over the course of the month.
Average Water Temperature in December
Temperatures in Signal Hill are sufficiently warm year round that it is not entirely meaningful to discuss the growing season in these terms. We nevertheless include the chart below as an illustration of the distribution of temperatures experienced throughout the year.
Time Spent in Various Temperature Bands and the Growing Season in December
The average accumulated growing degree days in Signal Hill are increasing during December, increasing by 205°F, from 4,806°F to 5,011°F, over the course of the month.
Growing Degree Days in December
The average daily incident shortwave solar energy in Signal Hill is essentially constant during December, remaining within 0.2 kWh of 3.1 kWh throughout.
The lowest average daily incident shortwave solar energy during December is 3.0 kWh on December 26.
Average Daily Incident Shortwave Solar Energy in December
For the purposes of this report, the geographical coordinates of Signal Hill are 33.804 deg latitude, -118.168 deg longitude, and 36 ft elevation.
The topography within 2 miles of Signal Hill contains only modest variations in elevation, with a maximum elevation change of 348 feet and an average elevation above sea level of 56 feet. Within 10 miles contains only modest variations in elevation (978 feet). Within 50 miles contains very significant variations in elevation (10,062 feet).
The area within 2 miles of Signal Hill is covered by artificial surfaces (98%), within 10 miles by artificial surfaces (75%) and water (22%), and within 50 miles by water (44%) and shrubs (26%).
This report illustrates the typical weather in Signal Hill 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 Signal Hill.
For each station, the records are corrected for the elevation difference between that station and Signal Hill 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 Signal Hill is computed as the weighted average of the individual contributions from each station, with weights proportional to the inverse of the distance between Signal Hill and a given station.
The stations contributing to this reconstruction are: Long Beach Airport (71%, 2.2 kilometers, northeast); Long Beach (26%, 4.2 kilometers, south); and Jack Northrop Field/Hawthorne Municipal Airport (2.5%, 20 kilometers, northwest).
Time zones for aiports and weather stations are provided by AskGeo.com .