December Weather at Siskiyou County Airport California, United StatesDaily high temperatures decrease by 3°F, from 47°F to 43°F, rarely falling below 35°F or exceeding 55°F. The lowest daily average high temperature is 43°F on December 25. Daily low temperatures decrease by 2°F, from 29°F to 27°F, rarely falling below 16°F or exceeding 40°F. The lowest daily average low temperature is 27°F on December 22. For reference, on August 2, the hottest day of the year, temperatures at Siskiyou County Airport typically range from 55°F to 92°F, while on December 22, the coldest day of the year, they range from 27°F to 43°F. 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. CloudsThe month of December at Siskiyou County Airport 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 12, with clear, mostly clear, or partly cloudy conditions 36% of the time. For reference, on January 9, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 66%, while on August 2, the clearest day of the year, the chance of clear, mostly clear, or partly cloudy skies is 88%. PrecipitationA wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. At Siskiyou County Airport, the chance of a wet day over the course of December is decreasing, starting the month at 37% and ending it at 32%. For reference, the year's highest daily chance of a wet day is 38% on December 4, and its lowest chance is 3% on August 3. Over the course of December at Siskiyou County Airport, the chance of a day with only rain decreases from 31% to 23%, the chance of a day with mixed snow and rain remains an essentially constant 7% throughout, and the chance of a day with only snow remains an essentially constant 2% throughout. RainfallTo 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 at Siskiyou County Airport is gradually decreasing, starting the month at 4.1 inches, when it rarely exceeds 8.4 inches or falls below 0.8 inches, and ending the month at 3.7 inches, when it rarely exceeds 8.4 inches or falls below 0.6 inches. The highest average 31-day accumulation is 4.2 inches on December 9. SnowfallAs with rainfall, we consider the snowfall accumulated over a sliding 31-day period centered around each day. The average sliding 31-day snowfall during December at Siskiyou County Airport is increasing, starting the month at 2.1 inches, when it rarely exceeds 5.3 inches, and ending the month at 3.1 inches, when it rarely exceeds 8.6 inches. The highest average 31-day accumulation is 3.1 inches on December 29. SunOver the course of December at Siskiyou County Airport, the length of the day is essentially constant. The shortest day of the month is December 20, with 9 hours, 8 minutes of daylight and the longest day is December 1, with 9 hours, 21 minutes of daylight. The earliest sunrise of the month at Siskiyou County Airport is 7:18 AM on December 1 and the latest sunrise is 19 minutes later at 7:37 AM on December 31. The earliest sunset is 4:38 PM on December 7 and the latest sunset is 10 minutes later at 4:49 PM on December 31. Daylight saving time is observed at Siskiyou County Airport during 2024, but it neither starts nor ends during December, so the entire month is in daylight saving time. For reference, on June 20, the longest day of the year, the Sun rises at 5:35 AM and sets 15 hours, 13 minutes later, at 8:48 PM, while on December 21, the shortest day of the year, it rises at 7:34 AM and sets 9 hours, 8 minutes later, at 4:42 PM. The figure below presents a compact representation of the sun's elevation (the angle of the sun above the horizon) and azimuth (its compass bearing) for every hour of every day in the reporting period. The horizontal axis is the day of the year and the vertical axis is the hour of the day. For a given day and hour of that day, the background color indicates the azimuth of the sun at that moment. The black isolines are contours of constant solar elevation. MoonThe figure below presents a compact representation of key lunar data for December 2024. The horizontal axis is the day, the vertical axis is the hour of the day, and the colored areas indicate when the moon is above the horizon. The vertical gray bars (new Moons) and blue bars (full Moons) indicate key Moon phases. The label associated with each bar indicates the date and time that the phase is obtained, and the companion time labels indicate the rise and set times of the Moon for the nearest time interval in which the moon is above the horizon.
HumidityWe base the humidity comfort level on the dew point, as it determines whether perspiration will evaporate from the skin, thereby cooling the body. Lower dew points feel drier and higher dew points feel more humid. Unlike temperature, which typically varies significantly between night and day, dew point tends to change more slowly, so while the temperature may drop at night, a muggy day is typically followed by a muggy night. The chance that a given day will be muggy at Siskiyou County Airport 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. WindThis section discusses the wide-area hourly average wind vector (speed and direction) at 10 meters above the ground. The wind experienced at any given location is highly dependent on local topography and other factors, and instantaneous wind speed and direction vary more widely than hourly averages. The average hourly wind speed at Siskiyou County Airport is essentially constant during December, remaining within 0.1 miles per hour of 4.9 miles per hour throughout. For reference, on February 19, the windiest day of the year, the daily average wind speed is 5.0 miles per hour, while on August 2, the calmest day of the year, the daily average wind speed is 4.0 miles per hour. The highest daily average wind speed during December is 5.0 miles per hour on December 13. The hourly average wind direction at Siskiyou County Airport throughout December is predominantly from the south, with a peak proportion of 41% on December 15. Growing SeasonDefinitions of the growing season vary throughout the world, but for the purposes of this report, we define it as the longest continuous period of non-freezing temperatures (≥ 32°F) in the year (the calendar year in the Northern Hemisphere, or from July 1 until June 30 in the Southern Hemisphere). The growing season at Siskiyou County Airport typically lasts for 5.0 months (155 days), from around May 7 to around October 9, rarely starting before April 20 or after May 25, and rarely ending before September 20 or after October 27. The month of December at Siskiyou County Airport is reliably fully outside of the growing season. Growing degree days are a measure of yearly heat accumulation used to predict plant and animal development, and defined as the integral of warmth above a base temperature, discarding any excess above a maximum temperature. In this report, we use a base of 50°F and a cap of 86°F. The average accumulated growing degree days at Siskiyou County Airport are essentially constant during December, remaining within 1°F of 2,800°F throughout. Solar EnergyThis section discusses the total daily incident shortwave solar energy reaching the surface of the ground over a wide area, taking full account of seasonal variations in the length of the day, the elevation of the Sun above the horizon, and absorption by clouds and other atmospheric constituents. Shortwave radiation includes visible light and ultraviolet radiation. The average daily incident shortwave solar energy at Siskiyou County Airport 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 19. TopographyFor the purposes of this report, the geographical coordinates of Siskiyou County Airport are 41.781 deg latitude, -122.469 deg longitude, and 2,648 ft elevation. The topography within 2 miles of Siskiyou County Airport contains only modest variations in elevation, with a maximum elevation change of 197 feet and an average elevation above sea level of 2,668 feet. Within 10 miles contains only modest variations in elevation (3,497 feet). Within 50 miles also contains extreme variations in elevation (13,173 feet). The area within 2 miles of Siskiyou County Airport is covered by cropland (55%), grassland (33%), and shrubs (12%), within 10 miles by shrubs (55%) and grassland (28%), and within 50 miles by trees (46%) and shrubs (43%). Data SourcesThis report illustrates the typical weather at Siskiyou County Airport, based on a statistical analysis of historical hourly weather reports and model reconstructions from January 1, 1980 to December 31, 2016. Temperature and Dew PointSiskiyou County Airport has a weather station that reported reliably enough during the analysis period that we have included it in our network. When available, historical temperature and dew point measurements are taken directly from this weather station. These records are obtained from NOAA's Integrated Surface Hourly data set, falling back on ICAO METAR records as required. In the case of missing or erroneous measurements from this station, we fall back on records from nearby stations, adjusted according to typical seasonal and diurnal intra-station differences. For a given day of the year and hour of the day, the fallback station is selected to minimize the prediction error over the years for which there are measurements for both stations. The stations on which we may fall back include but are not limited to Mount Shasta, Rogue Valley International - Medford Airport, Klamath Falls Airport, Sexton Summit,, Redding Municipal Airport, Red Bluff Municipal Airport, Jack Mc Namara Field, and Brookings Airport. Other DataAll data relating to the Sun's position (e.g., sunrise and sunset) are computed using astronomical formulas from the book, Astronomical Algorithms 2nd Edition , by Jean Meeus. All other weather data, including cloud cover, precipitation, wind speed and direction, and solar flux, come from NASA's MERRA-2 Modern-Era Retrospective Analysis . This reanalysis combines a variety of wide-area measurements in a state-of-the-art global meteorological model to reconstruct the hourly history of weather throughout the world on a 50-kilometer grid. Land Use data comes from the Global Land Cover SHARE database , published by the Food and Agriculture Organization of the United Nations. Elevation data comes from the Shuttle Radar Topography Mission (SRTM) , published by NASA's Jet Propulsion Laboratory. Names, locations, and time zones of places and some airports come from the GeoNames Geographical Database . Time zones for airports and weather stations are provided by AskGeo.com . Maps are © OpenStreetMap contributors. DisclaimerThe information on this site is provided as is, without any assurances as to its accuracy or suitability for any purpose. Weather data is prone to errors, outages, and other defects. We assume no responsibility for any decisions made on the basis of the content presented on this site. We draw particular cautious attention to our reliance on the MERRA-2 model-based reconstructions for a number of important data series. While having the tremendous advantages of temporal and spatial completeness, these reconstructions: (1) are based on computer models that may have model-based errors, (2) are coarsely sampled on a 50 km grid and are therefore unable to reconstruct the local variations of many microclimates, and (3) have particular difficulty with the weather in some coastal areas, especially small islands. 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