Average Weather in January in Westwood California, United States
In Westwood, the month of January is characterized by gradually rising daily high temperatures, with daily highs increasing by 3°F, from 39°F to 41°F over the course of the month, and rarely exceeding 51°F or dropping below 31°F.
Daily low temperatures are around 27°F, rarely falling below 15°F or exceeding 35°F.
For reference, on August 3, the hottest day of the year, temperatures in Westwood typically range from 55°F to 81°F, while on January 1, the coldest day of the year, they range from 26°F to 39°F.
Average High and Low Temperature in January
The figure below shows you a compact characterization of the hourly average temperatures for the quarter of the year centered on January. 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 January
The month of January in Westwood experiences essentially constant cloud cover, with the percentage of time that the sky is overcast or mostly cloudy remaining about 59% throughout the month.
The clearest day of the month is January 27, with clear, mostly clear, or partly cloudy conditions 42% of the time.
For reference, on February 27, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 61%, while on July 30, the clearest day of the year, the chance of clear, mostly clear, or partly cloudy skies is 89%.
Cloud Cover in January
A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. In Westwood, the chance of a wet day over the course of January is essentially constant, remaining around 32% throughout.
For reference, the year's highest daily chance of a wet day is 37% on March 1, and its lowest chance is 2% on August 3.
Over the course of January in Westwood, the chance of a day with only rain increases from 13% to 16%, the chance of a day with mixed snow and rain remains an essentially constant 12% throughout, and the chance of a day with only snow remains an essentially constant 5% throughout.
Probability of Precipitation in January
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 January in Westwood is essentially constant, remaining about 3.8 inches throughout, and rarely exceeding 8.6 inches or falling below 0.2 inches.
The lowest average 31-day accumulation is 3.7 inches on January 10.
Average Monthly Rainfall in January
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 January in Westwood is gradually decreasing, starting the month at 1.2 inches, when it rarely exceeds 2.9 inches, and ending the month at 0.9 inches, when it rarely exceeds 2.4 inches.
The highest average 31-day liquid-equivalent accumulation is 1.2 inches on January 1.
Average Monthly Liquid-Equivalent Snowfall in January
Over the course of January in Westwood, the length of the day is increasing. From the start to the end of the month, the length of the day increases by 46 minutes, implying an average daily increase of 1 minute, 32 seconds, and weekly increase of 10 minutes, 43 seconds.
The shortest day of the month is January 1, with 9 hours, 22 minutes of daylight and the longest day is January 31, with 10 hours, 8 minutes of daylight.
Hours of Daylight and Twilight in January
The latest sunrise of the month in Westwood is 7:26 AM on January 5 and the earliest sunrise is 13 minutes earlier at 7:13 AM on January 31.
The earliest sunset is 4:49 PM on January 1 and the latest sunset is 33 minutes later at 5:21 PM on January 31.
Daylight saving time is observed in Westwood during 2017, but it neither starts nor ends during January, so the entire month is in standard time.
For reference, on June 21, the longest day of the year, the Sun rises at 5:34 AM and sets 15 hours, 3 minutes later, at 8:37 PM, while on December 21, the shortest day of the year, it rises at 7:23 AM and sets 9 hours, 18 minutes later, at 4:41 PM.
Sunrise & Sunset with Twilight in January
We 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 in Westwood is essentially constant during January, remaining around 0% throughout.
Humidity Comfort Levels in January
This 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 in Westwood is essentially constant during January, remaining around 3.0 miles per hour throughout.
For reference, on December 18, the windiest day of the year, the daily average wind speed is 3.1 miles per hour, while on August 6, the calmest day of the year, the daily average wind speed is 2.4 miles per hour.
The lowest daily average wind speed during January is 2.9 miles per hour on January 20.
Average Wind Speed in January
Wind Direction in January
This 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 in Westwood is gradually increasing during January, rising by 0.7 kWh, from 2.1 kWh to 2.8 kWh, over the course of the month.
Average Daily Incident Shortwave Solar Energy in January
For the purposes of this report, the geographical coordinates of Westwood are 40.306 deg latitude, -121.006 deg longitude, and 5,125 ft elevation.
The topography within 2 miles of Westwood contains only modest variations in elevation, with a maximum elevation change of 213 feet and an average elevation above sea level of 5,112 feet. Within 10 miles contains only modest variations in elevation (3,960 feet). Within 50 miles also contains extreme variations in elevation (9,862 feet).
The area within 2 miles of Westwood is covered by trees (72%) and shrubs (27%), within 10 miles by trees (80%), and within 50 miles by trees (60%) and shrubs (34%).
This report illustrates the typical weather in Westwood 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 4 weather stations near enough to contribute to our estimation of the temperature and dew point in Westwood.
For each station, the records are corrected for the elevation difference between that station and Westwood 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 Westwood is computed as the weighted average of the individual contributions from each station, with weights proportional to the inverse of the distance between Westwood and a given station.
The stations contributing to this reconstruction are: Chico Municipal Airport (19%, 91 kilometers, southwest); Redding Municipal Airport (18%, 112 kilometers, west); Blue Canyon-Nyack Airport (35%, 117 kilometers, south); and Alturas Municipal Airport (27%, 137 kilometers, north).
All data relating to the Sun's position (e.g., sunrise and sunset) are computed using astronomical formulas from the book, Astronomical Tables of the Sun, Moon and Planets , 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 aiports and weather stations are provided by AskGeo.com .
Maps are © Esri, with data from National Geographic, Esri, DeLorme, NAVTEQ, UNEP-WCMC, USGS, NASA, ESA, METI, NRCAN, GEBCO, NOAA, and iPC.